root/Source/core/dom/Element.cpp

DEFINITIONS

1. attrNodeListMap
2. attrNodeListForElement
3. ensureAttrNodeListForElement
4. removeAttrNodeListForElement
5. findAttrNodeInList
6. create
7. elementRareData
8. ensureElementRareData
9. hasElementFlagInternal
10. setElementFlag
11. clearElementFlag
12. clearTabIndexExplicitlyIfNeeded
13. setTabIndexExplicitly
14. tabIndex
15. rendererIsFocusable
16. cloneNode
17. cloneElementWithChildren
18. cloneElementWithoutChildren
19. cloneElementWithoutAttributesAndChildren
20. detachAttribute
21. detachAttrNodeAtIndex
22. removeAttribute
23. setBooleanAttribute
24. attributes
25. activeAnimations
26. ensureActiveAnimations
27. hasActiveAnimations
28. nodeType
29. hasAttribute
30. synchronizeAllAttributes
31. synchronizeAttribute
32. synchronizeAttribute
33. getAttribute
34. scrollIntoView
35. scrollIntoViewIfNeeded
36. scrollByUnits
37. scrollByLines
38. scrollByPages
39. localZoomForRenderer
40. adjustForLocalZoom
41. offsetLeft
42. offsetTop
43. offsetWidth
44. offsetHeight
45. offsetParentForBindings
46. offsetParent
47. clientLeft
48. clientTop
49. clientWidth
50. clientHeight
51. scrollLeft
52. scrollTop
53. setScrollLeft
54. setScrollLeft
55. setScrollTop
56. setScrollTop
57. scrollWidth
58. scrollHeight
59. boundsInRootViewSpace
60. getClientRects
61. getBoundingClientRect
62. screenRect
63. getAttribute
64. getAttributeNS
65. setAttribute
66. setAttribute
67. setSynchronizedLazyAttribute
68. setAttributeInternal
69. makeIdForStyleResolution
70. attributeChanged
71. hasLegalLinkAttribute
72. subResourceAttributeName
73. attributeChangedFromParserOrByCloning
74. classStringHasClassName
75. classStringHasClassName
76. classAttributeChanged
77. shouldInvalidateDistributionWhenAttributeChanged
78. isEventHandlerAttribute
79. isJavaScriptURLAttribute
80. stripScriptingAttributes
81. parserSetAttributes
82. hasAttributes
83. hasEquivalentAttributes
84. nodeName
85. setPrefix
86. locateNamespacePrefix
87. baseURI
88. imageSourceURL
89. rendererIsNeeded
90. createRenderer
91. insertedInto
92. removedFrom
93. attach
94. detach
95. pseudoStyleCacheIsInvalid
96. styleForRenderer
97. originalStyleForRenderer
98. recalcStyle
99. recalcOwnStyle
100. recalcChildStyle
101. updateCallbackSelectors
102. addCallbackSelectors
103. removeCallbackSelectors
104. shadow
105. ensureShadow
106. didAffectSelector
107. setAnimationStyleChange
108. setNeedsAnimationStyleRecalc
109. setCustomElementDefinition
110. customElementDefinition
111. createShadowRoot
112. shadowRoot
113. didAddShadowRoot
114. userAgentShadowRoot
115. ensureUserAgentShadowRoot
116. childTypeAllowed
117. checkForEmptyStyleChange
118. checkForSiblingStyleChanges
119. childrenChanged
120. removeAllEventListeners
121. finishParsingChildren
122. formatForDebugger
123. attrNodeList
124. setAttributeNode
125. removeAttributeNode
126. parseAttributeName
127. setAttributeNS
128. removeAttributeInternal
129. addAttributeInternal
130. removeAttribute
131. removeAttributeNS
132. getAttributeNode
133. getAttributeNodeNS
134. hasAttribute
135. hasAttributeNS
136. focus
137. updateFocusAppearance
138. blur
139. isFocusable
140. isKeyboardFocusable
141. isMouseFocusable
142. dispatchFocusEvent
143. dispatchBlurEvent
144. dispatchFocusInEvent
145. dispatchFocusOutEvent
146. innerHTML
147. outerHTML
148. setInnerHTML
149. setOuterHTML
150. insertAdjacent
151. contextElementForInsertion
152. insertAdjacentElement
153. insertAdjacentText
154. insertAdjacentHTML
155. innerText
156. outerText
157. textFromChildren
158. shadowPseudoId
159. setShadowPseudoId
160. isInDescendantTreeOf
161. minimumSizeForResizing
162. setMinimumSizeForResizing
163. computedStyle
164. setChildIndex
165. rareDataChildIndex
166. computeInheritedLanguage
167. locale
168. cancelFocusAppearanceUpdate
169. normalizeAttributes
170. updatePseudoElement
171. createPseudoElementIfNeeded
172. pseudoElement
173. pseudoElementRenderer
174. matches
175. classList
176. dataset
177. getURLAttribute
178. getNonEmptyURLAttribute
179. getIntegralAttribute
180. setIntegralAttribute
181. getUnsignedIntegralAttribute
182. setUnsignedIntegralAttribute
183. getFloatingPointAttribute
184. setFloatingPointAttribute
185. webkitRequestFullscreen
186. webkitRequestFullScreen
187. setContainsFullScreenElement
188. parentCrossingFrameBoundaries
189. setContainsFullScreenElementOnAncestorsCrossingFrameBoundaries
190. setIsInTopLayer
191. webkitRequestPointerLock
192. spellcheckAttributeState
193. isSpellCheckingEnabled
194. fastAttributeLookupAllowed
195. hasNamedNodeMap
196. updateName
197. updateId
198. updateId
199. updateLabel
200. willModifyAttribute
201. didAddAttribute
202. didModifyAttribute
203. didRemoveAttribute
204. needsURLResolutionForInlineStyle
205. reResolveURLsInInlineStyle
206. didMoveToNewDocument
207. updateNamedItemRegistration
208. updateExtraNamedItemRegistration
209. ensureCachedHTMLCollection
210. scheduleLayerUpdate
211. cachedHTMLCollection
212. savedLayerScrollOffset
213. setSavedLayerScrollOffset
214. attrIfExists
215. ensureAttr
216. detachAttrNodeFromElementWithValue
217. detachAllAttrNodesFromElement
218. willRecalcStyle
219. didRecalcStyle
220. customStyleForRenderer
221. cloneAttributesFromElement
222. cloneDataFromElement
223. createUniqueElementData
224. inputMethodContext
225. hasInputMethodContext
226. synchronizeStyleAttributeInternal
227. style
228. ensureMutableInlineStyle
229. clearMutableInlineStyleIfEmpty
230. setInlineStyleFromString
231. styleAttributeChanged
232. inlineStyleChanged
233. setInlineStyleProperty
234. setInlineStyleProperty
235. setInlineStyleProperty
236. setInlineStyleProperty
237. removeInlineStyleProperty
238. removeAllInlineStyleProperties
239. updatePresentationAttributeStyle
240. addPropertyToPresentationAttributeStyle
241. addPropertyToPresentationAttributeStyle
242. addPropertyToPresentationAttributeStyle
243. supportsStyleSharing

/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 1999 Antti Koivisto (koivisto@kde.org)
 *           (C) 2001 Peter Kelly (pmk@post.com)
 *           (C) 2001 Dirk Mueller (mueller@kde.org)
 *           (C) 2007 David Smith (catfish.man@gmail.com)
 * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
 *           (C) 2007 Eric Seidel (eric@webkit.org)
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#include "config.h"
#include "core/dom/Element.h"

#include "CSSValueKeywords.h"
#include "RuntimeEnabledFeatures.h"
#include "SVGNames.h"
#include "XMLNames.h"
#include "bindings/v8/Dictionary.h"
#include "bindings/v8/ExceptionMessages.h"
#include "bindings/v8/ExceptionState.h"
#include "core/accessibility/AXObjectCache.h"
#include "core/animation/DocumentTimeline.h"
#include "core/animation/css/CSSAnimations.h"
#include "core/css/CSSImageValue.h"
#include "core/css/CSSStyleSheet.h"
#include "core/css/CSSValuePool.h"
#include "core/css/PropertySetCSSStyleDeclaration.h"
#include "core/css/StylePropertySet.h"
#include "core/css/parser/BisonCSSParser.h"
#include "core/css/resolver/StyleResolver.h"
#include "core/css/resolver/StyleResolverParentScope.h"
#include "core/dom/Attr.h"
#include "core/dom/CSSSelectorWatch.h"
#include "core/dom/ClientRect.h"
#include "core/dom/ClientRectList.h"
#include "core/dom/DatasetDOMStringMap.h"
#include "core/dom/ElementDataCache.h"
#include "core/dom/ElementRareData.h"
#include "core/dom/ElementTraversal.h"
#include "core/dom/ExceptionCode.h"
#include "core/dom/FullscreenElementStack.h"
#include "core/dom/MutationObserverInterestGroup.h"
#include "core/dom/MutationRecord.h"
#include "core/dom/NamedNodeMap.h"
#include "core/dom/NodeRenderStyle.h"
#include "core/dom/PresentationAttributeStyle.h"
#include "core/dom/PseudoElement.h"
#include "core/dom/RenderTreeBuilder.h"
#include "core/dom/ScriptableDocumentParser.h"
#include "core/dom/SelectorQuery.h"
#include "core/dom/Text.h"
#include "core/dom/custom/CustomElement.h"
#include "core/dom/custom/CustomElementRegistrationContext.h"
#include "core/dom/shadow/InsertionPoint.h"
#include "core/dom/shadow/ShadowRoot.h"
#include "core/editing/FrameSelection.h"
#include "core/editing/TextIterator.h"
#include "core/editing/htmlediting.h"
#include "core/editing/markup.h"
#include "core/events/EventDispatcher.h"
#include "core/events/FocusEvent.h"
#include "core/frame/FrameView.h"
#include "core/frame/LocalFrame.h"
#include "core/frame/UseCounter.h"
#include "core/frame/csp/ContentSecurityPolicy.h"
#include "core/html/ClassList.h"
#include "core/html/HTMLCollection.h"
#include "core/html/HTMLDocument.h"
#include "core/html/HTMLElement.h"
#include "core/html/HTMLFormControlsCollection.h"
#include "core/html/HTMLFrameElementBase.h"
#include "core/html/HTMLFrameOwnerElement.h"
#include "core/html/HTMLLabelElement.h"
#include "core/html/HTMLOptionsCollection.h"
#include "core/html/HTMLTableRowsCollection.h"
#include "core/html/HTMLTemplateElement.h"
#include "core/html/parser/HTMLParserIdioms.h"
#include "core/inspector/InspectorInstrumentation.h"
#include "core/page/FocusController.h"
#include "core/page/Page.h"
#include "core/page/PointerLockController.h"
#include "core/rendering/RenderLayer.h"
#include "core/rendering/RenderView.h"
#include "core/svg/SVGDocumentExtensions.h"
#include "core/svg/SVGElement.h"
#include "platform/scroll/ScrollableArea.h"
#include "wtf/BitVector.h"
#include "wtf/HashFunctions.h"
#include "wtf/text/CString.h"
#include "wtf/text/StringBuilder.h"
#include "wtf/text/TextPosition.h"

namespace WebCore {

using namespace HTMLNames;
using namespace XMLNames;

typedef Vector<RefPtr<Attr> > AttrNodeList;
typedef HashMap<Element*, OwnPtr<AttrNodeList> > AttrNodeListMap;

static AttrNodeListMap& attrNodeListMap()
{
    DEFINE_STATIC_LOCAL(AttrNodeListMap, map, ());
    return map;
}

static AttrNodeList* attrNodeListForElement(Element* element)
{
    if (!element->hasSyntheticAttrChildNodes())
        return 0;
    ASSERT(attrNodeListMap().contains(element));
    return attrNodeListMap().get(element);
}

static AttrNodeList& ensureAttrNodeListForElement(Element* element)
{
    if (element->hasSyntheticAttrChildNodes()) {
        ASSERT(attrNodeListMap().contains(element));
        return *attrNodeListMap().get(element);
    }
    ASSERT(!attrNodeListMap().contains(element));
    element->setHasSyntheticAttrChildNodes(true);
    AttrNodeListMap::AddResult result = attrNodeListMap().add(element, adoptPtr(new AttrNodeList));
    return *result.storedValue->value;
}

static void removeAttrNodeListForElement(Element* element)
{
    ASSERT(element->hasSyntheticAttrChildNodes());
    ASSERT(attrNodeListMap().contains(element));
    attrNodeListMap().remove(element);
    element->setHasSyntheticAttrChildNodes(false);
}

static Attr* findAttrNodeInList(const AttrNodeList& attrNodeList, const QualifiedName& name)
{
    AttrNodeList::const_iterator end = attrNodeList.end();
    for (AttrNodeList::const_iterator it = attrNodeList.begin(); it != end; ++it) {
        if ((*it)->qualifiedName() == name)
            return it->get();
    }
    return 0;
}

PassRefPtr<Element> Element::create(const QualifiedName& tagName, Document* document)
{
    return adoptRef(new Element(tagName, document, CreateElement));
}

Element::~Element()
{
    ASSERT(needsAttach());

    if (hasRareData())
        elementRareData()->clearShadow();

    if (isCustomElement())
        CustomElement::wasDestroyed(this);

    if (hasSyntheticAttrChildNodes())
        detachAllAttrNodesFromElement();

    if (hasPendingResources()) {
        document().accessSVGExtensions().removeElementFromPendingResources(this);
        ASSERT(!hasPendingResources());
    }
}

inline ElementRareData* Element::elementRareData() const
{
    ASSERT(hasRareData());
    return static_cast<ElementRareData*>(rareData());
}

inline ElementRareData& Element::ensureElementRareData()
{
    return static_cast<ElementRareData&>(ensureRareData());
}

bool Element::hasElementFlagInternal(ElementFlags mask) const
{
    return elementRareData()->hasElementFlag(mask);
}

void Element::setElementFlag(ElementFlags mask, bool value)
{
    if (!hasRareData() && !value)
        return;
    ensureElementRareData().setElementFlag(mask, value);
}

void Element::clearElementFlag(ElementFlags mask)
{
    if (!hasRareData())
        return;
    elementRareData()->clearElementFlag(mask);
}

void Element::clearTabIndexExplicitlyIfNeeded()
{
    if (hasRareData())
        elementRareData()->clearTabIndexExplicitly();
}

void Element::setTabIndexExplicitly(short tabIndex)
{
    ensureElementRareData().setTabIndexExplicitly(tabIndex);
}

short Element::tabIndex() const
{
    return hasRareData() ? elementRareData()->tabIndex() : 0;
}

bool Element::rendererIsFocusable() const
{
    // Elements in canvas fallback content are not rendered, but they are allowed to be
    // focusable as long as their canvas is displayed and visible.
    if (isInCanvasSubtree()) {
        const Element* e = this;
        while (e && !e->hasLocalName(canvasTag))
            e = e->parentElement();
        ASSERT(e);
        return e->renderer() && e->renderer()->style()->visibility() == VISIBLE;
    }

    // FIXME: These asserts should be in Node::isFocusable, but there are some
    // callsites like Document::setFocusedElement that would currently fail on
    // them. See crbug.com/251163
    if (!renderer()) {
        // We can't just use needsStyleRecalc() because if the node is in a
        // display:none tree it might say it needs style recalc but the whole
        // document is actually up to date.
        ASSERT(!document().childNeedsStyleRecalc());
    }

    // FIXME: Even if we are not visible, we might have a child that is visible.
    // Hyatt wants to fix that some day with a "has visible content" flag or the like.
    if (!renderer() || renderer()->style()->visibility() != VISIBLE)
        return false;

    return true;
}

PassRefPtr<Node> Element::cloneNode(bool deep)
{
    return deep ? cloneElementWithChildren() : cloneElementWithoutChildren();
}

PassRefPtr<Element> Element::cloneElementWithChildren()
{
    RefPtr<Element> clone = cloneElementWithoutChildren();
    cloneChildNodes(clone.get());
    return clone.release();
}

PassRefPtr<Element> Element::cloneElementWithoutChildren()
{
    RefPtr<Element> clone = cloneElementWithoutAttributesAndChildren();
    // This will catch HTML elements in the wrong namespace that are not correctly copied.
    // This is a sanity check as HTML overloads some of the DOM methods.
    ASSERT(isHTMLElement() == clone->isHTMLElement());

    clone->cloneDataFromElement(*this);
    return clone.release();
}

PassRefPtr<Element> Element::cloneElementWithoutAttributesAndChildren()
{
    return document().createElement(tagQName(), false);
}

PassRefPtr<Attr> Element::detachAttribute(size_t index)
{
    ASSERT(elementData());
    const Attribute& attribute = elementData()->attributeItem(index);
    RefPtr<Attr> attrNode = attrIfExists(attribute.name());
    if (attrNode)
        detachAttrNodeAtIndex(attrNode.get(), index);
    else {
        attrNode = Attr::create(document(), attribute.name(), attribute.value());
        removeAttributeInternal(index, NotInSynchronizationOfLazyAttribute);
    }
    return attrNode.release();
}

void Element::detachAttrNodeAtIndex(Attr* attr, size_t index)
{
    ASSERT(attr);
    ASSERT(elementData());

    const Attribute& attribute = elementData()->attributeItem(index);
    ASSERT(attribute.name() == attr->qualifiedName());
    detachAttrNodeFromElementWithValue(attr, attribute.value());
    removeAttributeInternal(index, NotInSynchronizationOfLazyAttribute);
}

void Element::removeAttribute(const QualifiedName& name)
{
    if (!elementData())
        return;

    size_t index = elementData()->getAttributeItemIndex(name);
    if (index == kNotFound)
        return;

    removeAttributeInternal(index, NotInSynchronizationOfLazyAttribute);
}

void Element::setBooleanAttribute(const QualifiedName& name, bool value)
{
    if (value)
        setAttribute(name, emptyAtom);
    else
        removeAttribute(name);
}

NamedNodeMap* Element::attributes() const
{
    ElementRareData& rareData = const_cast<Element*>(this)->ensureElementRareData();
    if (NamedNodeMap* attributeMap = rareData.attributeMap())
        return attributeMap;

    rareData.setAttributeMap(NamedNodeMap::create(const_cast<Element*>(this)));
    return rareData.attributeMap();
}

ActiveAnimations* Element::activeAnimations() const
{
    if (hasRareData())
        return elementRareData()->activeAnimations();
    return 0;
}

ActiveAnimations& Element::ensureActiveAnimations()
{
    ElementRareData& rareData = ensureElementRareData();
    if (!rareData.activeAnimations())
        rareData.setActiveAnimations(adoptPtrWillBeNoop(new ActiveAnimations()));
    return *rareData.activeAnimations();
}

bool Element::hasActiveAnimations() const
{
    if (!hasRareData())
        return false;

    ActiveAnimations* activeAnimations = elementRareData()->activeAnimations();
    return activeAnimations && !activeAnimations->isEmpty();
}

Node::NodeType Element::nodeType() const
{
    return ELEMENT_NODE;
}

bool Element::hasAttribute(const QualifiedName& name) const
{
    return hasAttributeNS(name.namespaceURI(), name.localName());
}

void Element::synchronizeAllAttributes() const
{
    if (!elementData())
        return;
    // NOTE: anyAttributeMatches in SelectorChecker.cpp
    // currently assumes that all lazy attributes have a null namespace.
    // If that ever changes we'll need to fix that code.
    if (elementData()->m_styleAttributeIsDirty) {
        ASSERT(isStyledElement());
        synchronizeStyleAttributeInternal();
    }
    if (elementData()->m_animatedSVGAttributesAreDirty) {
        ASSERT(isSVGElement());
        toSVGElement(this)->synchronizeAnimatedSVGAttribute(anyQName());
    }
}

inline void Element::synchronizeAttribute(const QualifiedName& name) const
{
    if (!elementData())
        return;
    if (UNLIKELY(name == styleAttr && elementData()->m_styleAttributeIsDirty)) {
        ASSERT(isStyledElement());
        synchronizeStyleAttributeInternal();
        return;
    }
    if (UNLIKELY(elementData()->m_animatedSVGAttributesAreDirty)) {
        ASSERT(isSVGElement());
        // See comment in the AtomicString version of synchronizeAttribute()
        // also.
        toSVGElement(this)->synchronizeAnimatedSVGAttribute(name);
    }
}

void Element::synchronizeAttribute(const AtomicString& localName) const
{
    // This version of synchronizeAttribute() is streamlined for the case where you don't have a full QualifiedName,
    // e.g when called from DOM API.
    if (!elementData())
        return;
    if (elementData()->m_styleAttributeIsDirty && equalPossiblyIgnoringCase(localName, styleAttr.localName(), shouldIgnoreAttributeCase())) {
        ASSERT(isStyledElement());
        synchronizeStyleAttributeInternal();
        return;
    }
    if (elementData()->m_animatedSVGAttributesAreDirty) {
        // We're not passing a namespace argument on purpose. SVGNames::*Attr are defined w/o namespaces as well.

        // FIXME: this code is called regardless of whether name is an
        // animated SVG Attribute. It would seem we should only call this method
        // if SVGElement::isAnimatableAttribute is true, but the list of
        // animatable attributes in isAnimatableAttribute does not suffice to
        // pass all layout tests. Also, m_animatedSVGAttributesAreDirty stays
        // dirty unless synchronizeAnimatedSVGAttribute is called with
        // anyQName(). This means that even if Element::synchronizeAttribute()
        // is called on all attributes, m_animatedSVGAttributesAreDirty remains
        // true.
        toSVGElement(this)->synchronizeAnimatedSVGAttribute(QualifiedName(nullAtom, localName, nullAtom));
    }
}

const AtomicString& Element::getAttribute(const QualifiedName& name) const
{
    if (!elementData())
        return nullAtom;
    synchronizeAttribute(name);
    if (const Attribute* attribute = getAttributeItem(name))
        return attribute->value();
    return nullAtom;
}

void Element::scrollIntoView(bool alignToTop)
{
    document().updateLayoutIgnorePendingStylesheets();

    if (!renderer())
        return;

    LayoutRect bounds = boundingBox();
    // Align to the top / bottom and to the closest edge.
    if (alignToTop)
        renderer()->scrollRectToVisible(bounds, ScrollAlignment::alignToEdgeIfNeeded, ScrollAlignment::alignTopAlways);
    else
        renderer()->scrollRectToVisible(bounds, ScrollAlignment::alignToEdgeIfNeeded, ScrollAlignment::alignBottomAlways);
}

void Element::scrollIntoViewIfNeeded(bool centerIfNeeded)
{
    document().updateLayoutIgnorePendingStylesheets();

    if (!renderer())
        return;

    LayoutRect bounds = boundingBox();
    if (centerIfNeeded)
        renderer()->scrollRectToVisible(bounds, ScrollAlignment::alignCenterIfNeeded, ScrollAlignment::alignCenterIfNeeded);
    else
        renderer()->scrollRectToVisible(bounds, ScrollAlignment::alignToEdgeIfNeeded, ScrollAlignment::alignToEdgeIfNeeded);
}

void Element::scrollByUnits(int units, ScrollGranularity granularity)
{
    document().updateLayoutIgnorePendingStylesheets();

    if (!renderer())
        return;

    if (!renderer()->hasOverflowClip())
        return;

    ScrollDirection direction = ScrollDown;
    if (units < 0) {
        direction = ScrollUp;
        units = -units;
    }
    toRenderBox(renderer())->scroll(direction, granularity, units);
}

void Element::scrollByLines(int lines)
{
    scrollByUnits(lines, ScrollByLine);
}

void Element::scrollByPages(int pages)
{
    scrollByUnits(pages, ScrollByPage);
}

static float localZoomForRenderer(RenderObject& renderer)
{
    // FIXME: This does the wrong thing if two opposing zooms are in effect and canceled each
    // other out, but the alternative is that we'd have to crawl up the whole render tree every
    // time (or store an additional bit in the RenderStyle to indicate that a zoom was specified).
    float zoomFactor = 1;
    if (renderer.style()->effectiveZoom() != 1) {
        // Need to find the nearest enclosing RenderObject that set up
        // a differing zoom, and then we divide our result by it to eliminate the zoom.
        RenderObject* prev = &renderer;
        for (RenderObject* curr = prev->parent(); curr; curr = curr->parent()) {
            if (curr->style()->effectiveZoom() != prev->style()->effectiveZoom()) {
                zoomFactor = prev->style()->zoom();
                break;
            }
            prev = curr;
        }
        if (prev->isRenderView())
            zoomFactor = prev->style()->zoom();
    }
    return zoomFactor;
}

static int adjustForLocalZoom(LayoutUnit value, RenderObject& renderer)
{
    float zoomFactor = localZoomForRenderer(renderer);
    if (zoomFactor == 1)
        return value;
    return lroundf(value / zoomFactor);
}

int Element::offsetLeft()
{
    document().updateLayoutIgnorePendingStylesheets();
    if (RenderBoxModelObject* renderer = renderBoxModelObject())
        return adjustForLocalZoom(renderer->pixelSnappedOffsetLeft(), *renderer);
    return 0;
}

int Element::offsetTop()
{
    document().updateLayoutIgnorePendingStylesheets();
    if (RenderBoxModelObject* renderer = renderBoxModelObject())
        return adjustForLocalZoom(renderer->pixelSnappedOffsetTop(), *renderer);
    return 0;
}

int Element::offsetWidth()
{
    document().updateRenderTreeForNodeIfNeeded(this);

    if (RenderBox* renderer = renderBox()) {
        if (renderer->canDetermineWidthWithoutLayout())
            return adjustLayoutUnitForAbsoluteZoom(renderer->fixedOffsetWidth(), *renderer).round();
    }

    document().updateLayoutIgnorePendingStylesheets();
    if (RenderBoxModelObject* renderer = renderBoxModelObject())
        return adjustLayoutUnitForAbsoluteZoom(renderer->pixelSnappedOffsetWidth(), *renderer).round();
    return 0;
}

int Element::offsetHeight()
{
    document().updateLayoutIgnorePendingStylesheets();
    if (RenderBoxModelObject* renderer = renderBoxModelObject())
        return adjustLayoutUnitForAbsoluteZoom(renderer->pixelSnappedOffsetHeight(), *renderer).round();
    return 0;
}

Element* Element::offsetParentForBindings()
{
    Element* element = offsetParent();
    if (!element || !element->isInShadowTree())
        return element;
    return element->containingShadowRoot()->shouldExposeToBindings() ? element : 0;
}

Element* Element::offsetParent()
{
    document().updateLayoutIgnorePendingStylesheets();
    if (RenderObject* renderer = this->renderer())
        return renderer->offsetParent();
    return 0;
}

int Element::clientLeft()
{
    document().updateLayoutIgnorePendingStylesheets();

    if (RenderBox* renderer = renderBox())
        return adjustForAbsoluteZoom(roundToInt(renderer->clientLeft()), renderer);
    return 0;
}

int Element::clientTop()
{
    document().updateLayoutIgnorePendingStylesheets();

    if (RenderBox* renderer = renderBox())
        return adjustForAbsoluteZoom(roundToInt(renderer->clientTop()), renderer);
    return 0;
}

int Element::clientWidth()
{
    document().updateLayoutIgnorePendingStylesheets();

    // When in strict mode, clientWidth for the document element should return the width of the containing frame.
    // When in quirks mode, clientWidth for the body element should return the width of the containing frame.
    bool inQuirksMode = document().inQuirksMode();
    if ((!inQuirksMode && document().documentElement() == this)
        || (inQuirksMode && isHTMLElement() && document().body() == this)) {
        if (FrameView* view = document().view()) {
            if (RenderView* renderView = document().renderView())
                return adjustForAbsoluteZoom(view->layoutSize().width(), renderView);
        }
    }

    if (RenderBox* renderer = renderBox())
        return adjustLayoutUnitForAbsoluteZoom(renderer->pixelSnappedClientWidth(), *renderer).round();
    return 0;
}

int Element::clientHeight()
{
    document().updateLayoutIgnorePendingStylesheets();

    // When in strict mode, clientHeight for the document element should return the height of the containing frame.
    // When in quirks mode, clientHeight for the body element should return the height of the containing frame.
    bool inQuirksMode = document().inQuirksMode();

    if ((!inQuirksMode && document().documentElement() == this)
        || (inQuirksMode && isHTMLElement() && document().body() == this)) {
        if (FrameView* view = document().view()) {
            if (RenderView* renderView = document().renderView())
                return adjustForAbsoluteZoom(view->layoutSize().height(), renderView);
        }
    }

    if (RenderBox* renderer = renderBox())
        return adjustLayoutUnitForAbsoluteZoom(renderer->pixelSnappedClientHeight(), *renderer).round();
    return 0;
}

int Element::scrollLeft()
{
    document().updateLayoutIgnorePendingStylesheets();

    if (document().documentElement() != this) {
        if (RenderBox* rend = renderBox())
            return adjustForAbsoluteZoom(rend->scrollLeft(), rend);
        return 0;
    }

    if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {
        if (document().inQuirksMode())
            return 0;

        if (FrameView* view = document().view()) {
            if (RenderView* renderView = document().renderView())
                return adjustForAbsoluteZoom(view->scrollX(), renderView);
        }
    }

    return 0;
}

int Element::scrollTop()
{
    document().updateLayoutIgnorePendingStylesheets();

    if (document().documentElement() != this) {
        if (RenderBox* rend = renderBox())
            return adjustForAbsoluteZoom(rend->scrollTop(), rend);
        return 0;
    }

    if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {
        if (document().inQuirksMode())
            return 0;

        if (FrameView* view = document().view()) {
            if (RenderView* renderView = document().renderView())
                return adjustForAbsoluteZoom(view->scrollY(), renderView);
        }
    }

    return 0;
}

void Element::setScrollLeft(int newLeft)
{
    document().updateLayoutIgnorePendingStylesheets();

    if (document().documentElement() != this) {
        if (RenderBox* rend = renderBox())
            rend->setScrollLeft(static_cast<int>(newLeft * rend->style()->effectiveZoom()));
        return;
    }

    if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {
        if (document().inQuirksMode())
            return;

        LocalFrame* frame = document().frame();
        if (!frame)
            return;
        FrameView* view = frame->view();
        if (!view)
            return;

        view->setScrollPosition(IntPoint(static_cast<int>(newLeft * frame->pageZoomFactor()), view->scrollY()));
    }
}

void Element::setScrollLeft(const Dictionary& scrollOptionsHorizontal, ExceptionState& exceptionState)
{
    String scrollBehaviorString;
    ScrollBehavior scrollBehavior = ScrollBehaviorAuto;
    if (scrollOptionsHorizontal.get("behavior", scrollBehaviorString)) {
        if (!ScrollableArea::scrollBehaviorFromString(scrollBehaviorString, scrollBehavior)) {
            exceptionState.throwTypeError("The ScrollBehavior provided is invalid.");
            return;
        }
    }

    int position;
    if (!scrollOptionsHorizontal.get("x", position)) {
        exceptionState.throwTypeError("ScrollOptionsHorizontal must include an 'x' member.");
        return;
    }

    // FIXME: Use scrollBehavior to decide whether to scroll smoothly or instantly.
    setScrollLeft(position);
}

void Element::setScrollTop(int newTop)
{
    document().updateLayoutIgnorePendingStylesheets();

    if (document().documentElement() != this) {
        if (RenderBox* rend = renderBox())
            rend->setScrollTop(static_cast<int>(newTop * rend->style()->effectiveZoom()));
        return;
    }

    if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {
        if (document().inQuirksMode())
            return;

        LocalFrame* frame = document().frame();
        if (!frame)
            return;
        FrameView* view = frame->view();
        if (!view)
            return;

        view->setScrollPosition(IntPoint(view->scrollX(), static_cast<int>(newTop * frame->pageZoomFactor())));
    }
}

void Element::setScrollTop(const Dictionary& scrollOptionsVertical, ExceptionState& exceptionState)
{
    String scrollBehaviorString;
    ScrollBehavior scrollBehavior = ScrollBehaviorAuto;
    if (scrollOptionsVertical.get("behavior", scrollBehaviorString)) {
        if (!ScrollableArea::scrollBehaviorFromString(scrollBehaviorString, scrollBehavior)) {
            exceptionState.throwTypeError("The ScrollBehavior provided is invalid.");
            return;
        }
    }

    int position;
    if (!scrollOptionsVertical.get("y", position)) {
        exceptionState.throwTypeError("ScrollOptionsVertical must include a 'y' member.");
        return;
    }

    // FIXME: Use scrollBehavior to decide whether to scroll smoothly or instantly.
    setScrollTop(position);
}

int Element::scrollWidth()
{
    document().updateLayoutIgnorePendingStylesheets();
    if (RenderBox* rend = renderBox())
        return adjustForAbsoluteZoom(rend->scrollWidth(), rend);
    return 0;
}

int Element::scrollHeight()
{
    document().updateLayoutIgnorePendingStylesheets();
    if (RenderBox* rend = renderBox())
        return adjustForAbsoluteZoom(rend->scrollHeight(), rend);
    return 0;
}

IntRect Element::boundsInRootViewSpace()
{
    document().updateLayoutIgnorePendingStylesheets();

    FrameView* view = document().view();
    if (!view)
        return IntRect();

    Vector<FloatQuad> quads;
    if (isSVGElement() && renderer()) {
        // Get the bounding rectangle from the SVG model.
        SVGElement* svgElement = toSVGElement(this);
        FloatRect localRect;
        if (svgElement->getBoundingBox(localRect))
            quads.append(renderer()->localToAbsoluteQuad(localRect));
    } else {
        // Get the bounding rectangle from the box model.
        if (renderBoxModelObject())
            renderBoxModelObject()->absoluteQuads(quads);
    }

    if (quads.isEmpty())
        return IntRect();

    IntRect result = quads[0].enclosingBoundingBox();
    for (size_t i = 1; i < quads.size(); ++i)
        result.unite(quads[i].enclosingBoundingBox());

    result = view->contentsToRootView(result);
    return result;
}

PassRefPtr<ClientRectList> Element::getClientRects()
{
    document().updateLayoutIgnorePendingStylesheets();

    RenderBoxModelObject* renderBoxModelObject = this->renderBoxModelObject();
    if (!renderBoxModelObject)
        return ClientRectList::create();

    // FIXME: Handle SVG elements.
    // FIXME: Handle table/inline-table with a caption.

    Vector<FloatQuad> quads;
    renderBoxModelObject->absoluteQuads(quads);
    document().adjustFloatQuadsForScrollAndAbsoluteZoom(quads, *renderBoxModelObject);
    return ClientRectList::create(quads);
}

PassRefPtr<ClientRect> Element::getBoundingClientRect()
{
    document().updateLayoutIgnorePendingStylesheets();

    Vector<FloatQuad> quads;
    if (isSVGElement() && renderer() && !renderer()->isSVGRoot()) {
        // Get the bounding rectangle from the SVG model.
        SVGElement* svgElement = toSVGElement(this);
        FloatRect localRect;
        if (svgElement->getBoundingBox(localRect))
            quads.append(renderer()->localToAbsoluteQuad(localRect));
    } else {
        // Get the bounding rectangle from the box model.
        if (renderBoxModelObject())
            renderBoxModelObject()->absoluteQuads(quads);
    }

    if (quads.isEmpty())
        return ClientRect::create();

    FloatRect result = quads[0].boundingBox();
    for (size_t i = 1; i < quads.size(); ++i)
        result.unite(quads[i].boundingBox());

    ASSERT(renderer());
    document().adjustFloatRectForScrollAndAbsoluteZoom(result, *renderer());
    return ClientRect::create(result);
}

IntRect Element::screenRect() const
{
    if (!renderer())
        return IntRect();
    // FIXME: this should probably respect transforms
    return document().view()->contentsToScreen(renderer()->absoluteBoundingBoxRectIgnoringTransforms());
}

const AtomicString& Element::getAttribute(const AtomicString& localName) const
{
    if (!elementData())
        return nullAtom;
    synchronizeAttribute(localName);
    if (const Attribute* attribute = elementData()->getAttributeItem(localName, shouldIgnoreAttributeCase()))
        return attribute->value();
    return nullAtom;
}

const AtomicString& Element::getAttributeNS(const AtomicString& namespaceURI, const AtomicString& localName) const
{
    return getAttribute(QualifiedName(nullAtom, localName, namespaceURI));
}

void Element::setAttribute(const AtomicString& localName, const AtomicString& value, ExceptionState& exceptionState)
{
    if (!Document::isValidName(localName)) {
        exceptionState.throwDOMException(InvalidCharacterError, "'" + localName + "' is not a valid attribute name.");
        return;
    }

    synchronizeAttribute(localName);
    const AtomicString& caseAdjustedLocalName = shouldIgnoreAttributeCase() ? localName.lower() : localName;

    size_t index = elementData() ? elementData()->getAttributeItemIndex(caseAdjustedLocalName, false) : kNotFound;
    const QualifiedName& qName = index != kNotFound ? attributeItem(index).name() : QualifiedName(nullAtom, caseAdjustedLocalName, nullAtom);
    setAttributeInternal(index, qName, value, NotInSynchronizationOfLazyAttribute);
}

void Element::setAttribute(const QualifiedName& name, const AtomicString& value)
{
    synchronizeAttribute(name);
    size_t index = elementData() ? elementData()->getAttributeItemIndex(name) : kNotFound;
    setAttributeInternal(index, name, value, NotInSynchronizationOfLazyAttribute);
}

void Element::setSynchronizedLazyAttribute(const QualifiedName& name, const AtomicString& value)
{
    size_t index = elementData() ? elementData()->getAttributeItemIndex(name) : kNotFound;
    setAttributeInternal(index, name, value, InSynchronizationOfLazyAttribute);
}

ALWAYS_INLINE void Element::setAttributeInternal(size_t index, const QualifiedName& name, const AtomicString& newValue, SynchronizationOfLazyAttribute inSynchronizationOfLazyAttribute)
{
    if (newValue.isNull()) {
        if (index != kNotFound)
            removeAttributeInternal(index, inSynchronizationOfLazyAttribute);
        return;
    }

    if (index == kNotFound) {
        addAttributeInternal(name, newValue, inSynchronizationOfLazyAttribute);
        return;
    }

    const Attribute& existingAttribute = attributeItem(index);
    QualifiedName existingAttributeName = existingAttribute.name();

    if (!inSynchronizationOfLazyAttribute)
        willModifyAttribute(existingAttributeName, existingAttribute.value(), newValue);

    if (newValue != existingAttribute.value()) {
        // If there is an Attr node hooked to this attribute, the Attr::setValue() call below
        // will write into the ElementData.
        // FIXME: Refactor this so it makes some sense.
        if (RefPtr<Attr> attrNode = inSynchronizationOfLazyAttribute ? nullptr : attrIfExists(existingAttributeName))
            attrNode->setValue(newValue);
        else
            ensureUniqueElementData().attributeItem(index).setValue(newValue);
    }

    if (!inSynchronizationOfLazyAttribute)
        didModifyAttribute(existingAttributeName, newValue);
}

static inline AtomicString makeIdForStyleResolution(const AtomicString& value, bool inQuirksMode)
{
    if (inQuirksMode)
        return value.lower();
    return value;
}

void Element::attributeChanged(const QualifiedName& name, const AtomicString& newValue, AttributeModificationReason reason)
{
    if (ElementShadow* parentElementShadow = shadowWhereNodeCanBeDistributed(*this)) {
        if (shouldInvalidateDistributionWhenAttributeChanged(parentElementShadow, name, newValue))
            parentElementShadow->setNeedsDistributionRecalc();
    }

    parseAttribute(name, newValue);

    document().incDOMTreeVersion();

    StyleResolver* styleResolver = document().styleResolver();
    bool testShouldInvalidateStyle = inActiveDocument() && styleResolver && styleChangeType() < SubtreeStyleChange;

    if (isStyledElement() && name == styleAttr) {
        styleAttributeChanged(newValue, reason);
    } else if (isStyledElement() && isPresentationAttribute(name)) {
        elementData()->m_presentationAttributeStyleIsDirty = true;
        setNeedsStyleRecalc(LocalStyleChange);
    }

    if (isIdAttributeName(name)) {
        AtomicString oldId = elementData()->idForStyleResolution();
        AtomicString newId = makeIdForStyleResolution(newValue, document().inQuirksMode());
        if (newId != oldId) {
            elementData()->setIdForStyleResolution(newId);
            if (testShouldInvalidateStyle)
                styleResolver->ensureUpdatedRuleFeatureSet().scheduleStyleInvalidationForIdChange(oldId, newId, *this);
        }
    } else if (name == classAttr) {
        classAttributeChanged(newValue);
    } else if (name == HTMLNames::nameAttr) {
        setHasName(!newValue.isNull());
    }

    invalidateNodeListCachesInAncestors(&name, this);

    // If there is currently no StyleResolver, we can't be sure that this attribute change won't affect style.
    if (!styleResolver)
        setNeedsStyleRecalc(SubtreeStyleChange);

    if (AXObjectCache* cache = document().existingAXObjectCache())
        cache->handleAttributeChanged(name, this);
}

bool Element::hasLegalLinkAttribute(const QualifiedName&) const
{
    return false;
}

const QualifiedName& Element::subResourceAttributeName() const
{
    return nullQName();
}

inline void Element::attributeChangedFromParserOrByCloning(const QualifiedName& name, const AtomicString& newValue, AttributeModificationReason reason)
{
    if (name == isAttr)
        CustomElementRegistrationContext::setTypeExtension(this, newValue);
    attributeChanged(name, newValue, reason);
}

template <typename CharacterType>
static inline bool classStringHasClassName(const CharacterType* characters, unsigned length)
{
    ASSERT(length > 0);

    unsigned i = 0;
    do {
        if (isNotHTMLSpace<CharacterType>(characters[i]))
            break;
        ++i;
    } while (i < length);

    return i < length;
}

static inline bool classStringHasClassName(const AtomicString& newClassString)
{
    unsigned length = newClassString.length();

    if (!length)
        return false;

    if (newClassString.is8Bit())
        return classStringHasClassName(newClassString.characters8(), length);
    return classStringHasClassName(newClassString.characters16(), length);
}

void Element::classAttributeChanged(const AtomicString& newClassString)
{
    StyleResolver* styleResolver = document().styleResolver();
    bool testShouldInvalidateStyle = inActiveDocument() && styleResolver && styleChangeType() < SubtreeStyleChange;

    ASSERT(elementData());
    if (classStringHasClassName(newClassString)) {
        const bool shouldFoldCase = document().inQuirksMode();
        const SpaceSplitString oldClasses = elementData()->classNames();
        elementData()->setClass(newClassString, shouldFoldCase);
        const SpaceSplitString& newClasses = elementData()->classNames();
        if (testShouldInvalidateStyle)
            styleResolver->ensureUpdatedRuleFeatureSet().scheduleStyleInvalidationForClassChange(oldClasses, newClasses, *this);
    } else {
        const SpaceSplitString& oldClasses = elementData()->classNames();
        if (testShouldInvalidateStyle)
            styleResolver->ensureUpdatedRuleFeatureSet().scheduleStyleInvalidationForClassChange(oldClasses, *this);
        elementData()->clearClass();
    }

    if (hasRareData())
        elementRareData()->clearClassListValueForQuirksMode();
}

bool Element::shouldInvalidateDistributionWhenAttributeChanged(ElementShadow* elementShadow, const QualifiedName& name, const AtomicString& newValue)
{
    ASSERT(elementShadow);
    const SelectRuleFeatureSet& featureSet = elementShadow->ensureSelectFeatureSet();

    if (isIdAttributeName(name)) {
        AtomicString oldId = elementData()->idForStyleResolution();
        AtomicString newId = makeIdForStyleResolution(newValue, document().inQuirksMode());
        if (newId != oldId) {
            if (!oldId.isEmpty() && featureSet.hasSelectorForId(oldId))
                return true;
            if (!newId.isEmpty() && featureSet.hasSelectorForId(newId))
                return true;
        }
    }

    if (name == HTMLNames::classAttr) {
        const AtomicString& newClassString = newValue;
        if (classStringHasClassName(newClassString)) {
            const bool shouldFoldCase = document().inQuirksMode();
            const SpaceSplitString& oldClasses = elementData()->classNames();
            const SpaceSplitString newClasses(newClassString, shouldFoldCase);
            if (featureSet.checkSelectorsForClassChange(oldClasses, newClasses))
                return true;
        } else {
            const SpaceSplitString& oldClasses = elementData()->classNames();
            if (featureSet.checkSelectorsForClassChange(oldClasses))
                return true;
        }
    }

    return featureSet.hasSelectorForAttribute(name.localName());
}

// Returns true is the given attribute is an event handler.
// We consider an event handler any attribute that begins with "on".
// It is a simple solution that has the advantage of not requiring any
// code or configuration change if a new event handler is defined.

static inline bool isEventHandlerAttribute(const Attribute& attribute)
{
    return attribute.name().namespaceURI().isNull() && attribute.name().localName().startsWith("on");
}

bool Element::isJavaScriptURLAttribute(const Attribute& attribute) const
{
    return isURLAttribute(attribute) && protocolIsJavaScript(stripLeadingAndTrailingHTMLSpaces(attribute.value()));
}

void Element::stripScriptingAttributes(Vector<Attribute>& attributeVector) const
{
    size_t destination = 0;
    for (size_t source = 0; source < attributeVector.size(); ++source) {
        if (isEventHandlerAttribute(attributeVector[source])
            || isJavaScriptURLAttribute(attributeVector[source])
            || isHTMLContentAttribute(attributeVector[source]))
            continue;

        if (source != destination)
            attributeVector[destination] = attributeVector[source];

        ++destination;
    }
    attributeVector.shrink(destination);
}

void Element::parserSetAttributes(const Vector<Attribute>& attributeVector)
{
    ASSERT(!inDocument());
    ASSERT(!parentNode());
    ASSERT(!m_elementData);

    if (attributeVector.isEmpty())
        return;

    if (document().elementDataCache())
        m_elementData = document().elementDataCache()->cachedShareableElementDataWithAttributes(attributeVector);
    else
        m_elementData = ShareableElementData::createWithAttributes(attributeVector);

    // Use attributeVector instead of m_elementData because attributeChanged might modify m_elementData.
    for (unsigned i = 0; i < attributeVector.size(); ++i)
        attributeChangedFromParserOrByCloning(attributeVector[i].name(), attributeVector[i].value(), ModifiedDirectly);
}

bool Element::hasAttributes() const
{
    synchronizeAllAttributes();
    return elementData() && elementData()->length();
}

bool Element::hasEquivalentAttributes(const Element* other) const
{
    synchronizeAllAttributes();
    other->synchronizeAllAttributes();
    if (elementData() == other->elementData())
        return true;
    if (elementData())
        return elementData()->isEquivalent(other->elementData());
    if (other->elementData())
        return other->elementData()->isEquivalent(elementData());
    return true;
}

String Element::nodeName() const
{
    return m_tagName.toString();
}

void Element::setPrefix(const AtomicString& prefix, ExceptionState& exceptionState)
{
    UseCounter::count(document(), UseCounter::ElementSetPrefix);

    if (!prefix.isEmpty() && !Document::isValidName(prefix)) {
        exceptionState.throwDOMException(InvalidCharacterError, "The prefix '" + prefix + "' is not a valid name.");
        return;
    }

    // FIXME: Raise NamespaceError if prefix is malformed per the Namespaces in XML specification.

    const AtomicString& nodeNamespaceURI = namespaceURI();
    if (nodeNamespaceURI.isEmpty() && !prefix.isEmpty()) {
        exceptionState.throwDOMException(NamespaceError, "No namespace is set, so a namespace prefix may not be set.");
        return;
    }

    if (prefix == xmlAtom && nodeNamespaceURI != XMLNames::xmlNamespaceURI) {
        exceptionState.throwDOMException(NamespaceError, "The prefix '" + xmlAtom + "' may not be set on namespace '" + nodeNamespaceURI + "'.");
        return;
    }

    if (exceptionState.hadException())
        return;

    m_tagName.setPrefix(prefix.isEmpty() ? AtomicString() : prefix);
}

const AtomicString& Element::locateNamespacePrefix(const AtomicString& namespaceToLocate) const
{
    if (!prefix().isNull() && namespaceURI() == namespaceToLocate)
        return prefix();

    if (hasAttributes()) {
        unsigned attributeCount = this->attributeCount();
        for (unsigned i = 0; i < attributeCount; ++i) {
            const Attribute& attr = attributeItem(i);

            if (attr.prefix() == xmlnsAtom && attr.value() == namespaceToLocate)
                return attr.localName();
        }
    }

    if (Element* parent = parentElement())
        return parent->locateNamespacePrefix(namespaceToLocate);

    return nullAtom;
}

KURL Element::baseURI() const
{
    const AtomicString& baseAttribute = fastGetAttribute(baseAttr);
    KURL base(KURL(), baseAttribute);
    if (!base.protocol().isEmpty())
        return base;

    ContainerNode* parent = parentNode();
    if (!parent)
        return base;

    const KURL& parentBase = parent->baseURI();
    if (parentBase.isNull())
        return base;

    return KURL(parentBase, baseAttribute);
}

const AtomicString Element::imageSourceURL() const
{
    return getAttribute(srcAttr);
}

bool Element::rendererIsNeeded(const RenderStyle& style)
{
    return style.display() != NONE;
}

RenderObject* Element::createRenderer(RenderStyle* style)
{
    return RenderObject::createObject(this, style);
}

Node::InsertionNotificationRequest Element::insertedInto(ContainerNode* insertionPoint)
{
    // need to do superclass processing first so inDocument() is true
    // by the time we reach updateId
    ContainerNode::insertedInto(insertionPoint);

    if (containsFullScreenElement() && parentElement() && !parentElement()->containsFullScreenElement())
        setContainsFullScreenElementOnAncestorsCrossingFrameBoundaries(true);

    ASSERT(!hasRareData() || !elementRareData()->hasPseudoElements());

    if (!insertionPoint->isInTreeScope())
        return InsertionDone;

    if (hasRareData())
        elementRareData()->clearClassListValueForQuirksMode();

    if (isUpgradedCustomElement() && inDocument())
        CustomElement::didEnterDocument(this, document());

    TreeScope& scope = insertionPoint->treeScope();
    if (scope != treeScope())
        return InsertionDone;

    const AtomicString& idValue = getIdAttribute();
    if (!idValue.isNull())
        updateId(scope, nullAtom, idValue);

    const AtomicString& nameValue = getNameAttribute();
    if (!nameValue.isNull())
        updateName(nullAtom, nameValue);

    if (isHTMLLabelElement(*this)) {
        if (scope.shouldCacheLabelsByForAttribute())
            updateLabel(scope, nullAtom, fastGetAttribute(forAttr));
    }

    if (parentElement() && parentElement()->isInCanvasSubtree())
        setIsInCanvasSubtree(true);

    return InsertionDone;
}

void Element::removedFrom(ContainerNode* insertionPoint)
{
    bool wasInDocument = insertionPoint->inDocument();

    ASSERT(!hasRareData() || !elementRareData()->hasPseudoElements());

    if (containsFullScreenElement())
        setContainsFullScreenElementOnAncestorsCrossingFrameBoundaries(false);

    if (document().page())
        document().page()->pointerLockController().elementRemoved(this);

    setSavedLayerScrollOffset(IntSize());

    if (insertionPoint->isInTreeScope() && treeScope() == document()) {
        const AtomicString& idValue = getIdAttribute();
        if (!idValue.isNull())
            updateId(insertionPoint->treeScope(), idValue, nullAtom);

        const AtomicString& nameValue = getNameAttribute();
        if (!nameValue.isNull())
            updateName(nameValue, nullAtom);

        if (isHTMLLabelElement(*this)) {
            TreeScope& treeScope = insertionPoint->treeScope();
            if (treeScope.shouldCacheLabelsByForAttribute())
                updateLabel(treeScope, fastGetAttribute(forAttr), nullAtom);
        }
    }

    ContainerNode::removedFrom(insertionPoint);
    if (wasInDocument) {
        if (hasPendingResources())
            document().accessSVGExtensions().removeElementFromPendingResources(this);

        if (isUpgradedCustomElement())
            CustomElement::didLeaveDocument(this, insertionPoint->document());
    }

    document().removeFromTopLayer(this);

    clearElementFlag(IsInCanvasSubtree);
}

void Element::attach(const AttachContext& context)
{
    ASSERT(document().inStyleRecalc());

    // We've already been through detach when doing an attach, but we might
    // need to clear any state that's been added since then.
    if (hasRareData() && styleChangeType() == NeedsReattachStyleChange) {
        ElementRareData* data = elementRareData();
        data->clearComputedStyle();
        data->clearRestyleFlags();
        // Only clear the style state if we're not going to reuse the style from recalcStyle.
        if (!context.resolvedStyle)
            data->resetStyleState();
    }

    RenderTreeBuilder(this, context.resolvedStyle).createRendererForElementIfNeeded();

    addCallbackSelectors();

    StyleResolverParentScope parentScope(*this);

    createPseudoElementIfNeeded(BEFORE);

    // When a shadow root exists, it does the work of attaching the children.
    if (ElementShadow* shadow = this->shadow())
        shadow->attach(context);

    ContainerNode::attach(context);

    createPseudoElementIfNeeded(AFTER);
    createPseudoElementIfNeeded(BACKDROP);

    if (hasRareData()) {
        ElementRareData* data = elementRareData();
        if (data->hasElementFlag(NeedsFocusAppearanceUpdateSoonAfterAttach)) {
            if (isFocusable() && document().focusedElement() == this)
                document().updateFocusAppearanceSoon(false /* don't restore selection */);
            data->clearElementFlag(NeedsFocusAppearanceUpdateSoonAfterAttach);
        }
        if (!renderer()) {
            if (ActiveAnimations* activeAnimations = data->activeAnimations()) {
                activeAnimations->cssAnimations().cancel();
                activeAnimations->setAnimationStyleChange(false);
            }
        }
    }

    InspectorInstrumentation::didRecalculateStyleForElement(this);
}

void Element::detach(const AttachContext& context)
{
    HTMLFrameOwnerElement::UpdateSuspendScope suspendWidgetHierarchyUpdates;
    cancelFocusAppearanceUpdate();
    removeCallbackSelectors();
    if (needsLayerUpdate())
        document().unscheduleLayerUpdate(*this);
    if (hasRareData()) {
        ElementRareData* data = elementRareData();
        data->clearPseudoElements();

        // attach() will perform the below steps for us when inside recalcStyle.
        if (!document().inStyleRecalc()) {
            data->resetStyleState();
            data->clearComputedStyle();
            data->clearRestyleFlags();
        }

        if (ActiveAnimations* activeAnimations = data->activeAnimations()) {
            if (context.performingReattach) {
                // FIXME: We call detach from withing style recalc, so compositingState is not up to date.
                // https://code.google.com/p/chromium/issues/detail?id=339847
                DisableCompositingQueryAsserts disabler;

                // FIXME: restart compositor animations rather than pull back to the main thread
                activeAnimations->cancelAnimationOnCompositor();
            } else {
                activeAnimations->cssAnimations().cancel();
                activeAnimations->setAnimationStyleChange(false);
            }
        }

        if (ElementShadow* shadow = data->shadow())
            shadow->detach(context);
    }
    ContainerNode::detach(context);
}

bool Element::pseudoStyleCacheIsInvalid(const RenderStyle* currentStyle, RenderStyle* newStyle)
{
    ASSERT(currentStyle == renderStyle());
    ASSERT(renderer());

    if (!currentStyle)
        return false;

    const PseudoStyleCache* pseudoStyleCache = currentStyle->cachedPseudoStyles();
    if (!pseudoStyleCache)
        return false;

    size_t cacheSize = pseudoStyleCache->size();
    for (size_t i = 0; i < cacheSize; ++i) {
        RefPtr<RenderStyle> newPseudoStyle;
        PseudoId pseudoId = pseudoStyleCache->at(i)->styleType();
        if (pseudoId == FIRST_LINE || pseudoId == FIRST_LINE_INHERITED)
            newPseudoStyle = renderer()->uncachedFirstLineStyle(newStyle);
        else
            newPseudoStyle = renderer()->getUncachedPseudoStyle(PseudoStyleRequest(pseudoId), newStyle, newStyle);
        if (!newPseudoStyle)
            return true;
        if (*newPseudoStyle != *pseudoStyleCache->at(i)) {
            if (pseudoId < FIRST_INTERNAL_PSEUDOID)
                newStyle->setHasPseudoStyle(pseudoId);
            newStyle->addCachedPseudoStyle(newPseudoStyle);
            if (pseudoId == FIRST_LINE || pseudoId == FIRST_LINE_INHERITED) {
                // FIXME: We should do an actual diff to determine whether a repaint vs. layout
                // is needed, but for now just assume a layout will be required. The diff code
                // in RenderObject::setStyle would need to be factored out so that it could be reused.
                renderer()->setNeedsLayoutAndPrefWidthsRecalc();
            }
            return true;
        }
    }
    return false;
}

PassRefPtr<RenderStyle> Element::styleForRenderer()
{
    ASSERT(document().inStyleRecalc());

    RefPtr<RenderStyle> style;

    // FIXME: Instead of clearing updates that may have been added from calls to styleForElement
    // outside recalcStyle, we should just never set them if we're not inside recalcStyle.
    if (ActiveAnimations* activeAnimations = this->activeAnimations())
        activeAnimations->cssAnimations().setPendingUpdate(nullptr);

    if (hasCustomStyleCallbacks())
        style = customStyleForRenderer();
    if (!style)
        style = originalStyleForRenderer();

    // styleForElement() might add active animations so we need to get it again.
    if (ActiveAnimations* activeAnimations = this->activeAnimations())
        activeAnimations->cssAnimations().maybeApplyPendingUpdate(this);

    ASSERT(style);
    return style.release();
}

PassRefPtr<RenderStyle> Element::originalStyleForRenderer()
{
    ASSERT(document().inStyleRecalc());
    return document().ensureStyleResolver().styleForElement(this);
}

void Element::recalcStyle(StyleRecalcChange change, Text* nextTextSibling)
{
    ASSERT(document().inStyleRecalc());
    ASSERT(!parentOrShadowHostNode()->needsStyleRecalc());

    if (hasCustomStyleCallbacks())
        willRecalcStyle(change);

    if (change >= Inherit || needsStyleRecalc()) {
        if (hasRareData()) {
            ElementRareData* data = elementRareData();
            data->resetStyleState();
            data->clearComputedStyle();

            if (change >= Inherit) {
                if (ActiveAnimations* activeAnimations = data->activeAnimations())
                    activeAnimations->setAnimationStyleChange(false);
            }
        }
        if (parentRenderStyle())
            change = recalcOwnStyle(change);
        clearNeedsStyleRecalc();
    }

    // If we reattached we don't need to recalc the style of our descendants anymore.
    if ((change >= UpdatePseudoElements && change < Reattach) || childNeedsStyleRecalc()) {
        recalcChildStyle(change);
        clearChildNeedsStyleRecalc();
    }

    if (hasCustomStyleCallbacks())
        didRecalcStyle(change);

    if (change == Reattach)
        reattachWhitespaceSiblings(nextTextSibling);
}

StyleRecalcChange Element::recalcOwnStyle(StyleRecalcChange change)
{
    ASSERT(document().inStyleRecalc());
    ASSERT(!parentOrShadowHostNode()->needsStyleRecalc());
    ASSERT(change >= Inherit || needsStyleRecalc());
    ASSERT(parentRenderStyle());

    RefPtr<RenderStyle> oldStyle = renderStyle();
    RefPtr<RenderStyle> newStyle = styleForRenderer();
    StyleRecalcChange localChange = RenderStyle::stylePropagationDiff(oldStyle.get(), newStyle.get());

    ASSERT(newStyle);

    if (localChange == Reattach) {
        AttachContext reattachContext;
        reattachContext.resolvedStyle = newStyle.get();
        bool rendererWillChange = needsAttach() || renderer();
        reattach(reattachContext);
        if (rendererWillChange || renderer())
            return Reattach;
        return ReattachNoRenderer;
    }

    ASSERT(oldStyle);

    InspectorInstrumentation::didRecalculateStyleForElement(this);

    if (localChange != NoChange)
        updateCallbackSelectors(oldStyle.get(), newStyle.get());

    if (RenderObject* renderer = this->renderer()) {
        if (localChange != NoChange || pseudoStyleCacheIsInvalid(oldStyle.get(), newStyle.get()) || needsLayerUpdate()) {
            renderer->setStyle(newStyle.get());
        } else {
            // Although no change occurred, we use the new style so that the cousin style sharing code won't get
            // fooled into believing this style is the same.
            // FIXME: We may be able to remove this hack, see discussion in
            // https://codereview.chromium.org/30453002/
            renderer->setStyleInternal(newStyle.get());
        }
    }

    if (styleChangeType() >= SubtreeStyleChange)
        return Force;

    if (change > Inherit || localChange > Inherit)
        return max(localChange, change);

    if (localChange < Inherit && (oldStyle->hasPseudoElementStyle() || newStyle->hasPseudoElementStyle()))
        return UpdatePseudoElements;

    return localChange;
}

void Element::recalcChildStyle(StyleRecalcChange change)
{
    ASSERT(document().inStyleRecalc());
    ASSERT(change >= UpdatePseudoElements || childNeedsStyleRecalc());
    ASSERT(!needsStyleRecalc());

    StyleResolverParentScope parentScope(*this);

    updatePseudoElement(BEFORE, change);

    if (change > UpdatePseudoElements || childNeedsStyleRecalc()) {
        for (ShadowRoot* root = youngestShadowRoot(); root; root = root->olderShadowRoot()) {
            if (root->shouldCallRecalcStyle(change))
                root->recalcStyle(change);
        }
    }

    if (change < Force && hasRareData() && childNeedsStyleRecalc())
        checkForChildrenAdjacentRuleChanges();

    if (change > UpdatePseudoElements || childNeedsStyleRecalc()) {
        // This loop is deliberately backwards because we use insertBefore in the rendering tree, and want to avoid
        // a potentially n^2 loop to find the insertion point while resolving style. Having us start from the last
        // child and work our way back means in the common case, we'll find the insertion point in O(1) time.
        // See crbug.com/288225
        StyleResolver& styleResolver = document().ensureStyleResolver();
        Text* lastTextNode = 0;
        for (Node* child = lastChild(); child; child = child->previousSibling()) {
            if (child->isTextNode()) {
                toText(child)->recalcTextStyle(change, lastTextNode);
                lastTextNode = toText(child);
            } else if (child->isElementNode()) {
                Element* element = toElement(child);
                if (element->shouldCallRecalcStyle(change))
                    element->recalcStyle(change, lastTextNode);
                else if (element->supportsStyleSharing())
                    styleResolver.addToStyleSharingList(*element);
                if (element->renderer())
                    lastTextNode = 0;
            }
        }
    }

    updatePseudoElement(AFTER, change);
    updatePseudoElement(BACKDROP, change);
}

void Element::updateCallbackSelectors(RenderStyle* oldStyle, RenderStyle* newStyle)
{
    Vector<String> emptyVector;
    const Vector<String>& oldCallbackSelectors = oldStyle ? oldStyle->callbackSelectors() : emptyVector;
    const Vector<String>& newCallbackSelectors = newStyle ? newStyle->callbackSelectors() : emptyVector;
    if (oldCallbackSelectors.isEmpty() && newCallbackSelectors.isEmpty())
        return;
    if (oldCallbackSelectors != newCallbackSelectors)
        CSSSelectorWatch::from(document()).updateSelectorMatches(oldCallbackSelectors, newCallbackSelectors);
}

void Element::addCallbackSelectors()
{
    updateCallbackSelectors(0, renderStyle());
}

void Element::removeCallbackSelectors()
{
    updateCallbackSelectors(renderStyle(), 0);
}

ElementShadow* Element::shadow() const
{
    return hasRareData() ? elementRareData()->shadow() : 0;
}

ElementShadow& Element::ensureShadow()
{
    return ensureElementRareData().ensureShadow();
}

void Element::didAffectSelector(AffectedSelectorMask mask)
{
    setNeedsStyleRecalc(SubtreeStyleChange);
    if (ElementShadow* elementShadow = shadowWhereNodeCanBeDistributed(*this))
        elementShadow->didAffectSelector(mask);
}

void Element::setAnimationStyleChange(bool animationStyleChange)
{
    if (ActiveAnimations* activeAnimations = elementRareData()->activeAnimations())
        activeAnimations->setAnimationStyleChange(animationStyleChange);
}

void Element::setNeedsAnimationStyleRecalc()
{
    if (styleChangeType() != NoStyleChange)
        return;

    setNeedsStyleRecalc(LocalStyleChange);
    setAnimationStyleChange(true);
}

void Element::setCustomElementDefinition(PassRefPtr<CustomElementDefinition> definition)
{
    if (!hasRareData() && !definition)
        return;
    ASSERT(!customElementDefinition());
    ensureElementRareData().setCustomElementDefinition(definition);
}

CustomElementDefinition* Element::customElementDefinition() const
{
    if (hasRareData())
        return elementRareData()->customElementDefinition();
    return 0;
}

PassRefPtr<ShadowRoot> Element::createShadowRoot(ExceptionState& exceptionState)
{
    if (alwaysCreateUserAgentShadowRoot())
        ensureUserAgentShadowRoot();

    // Some elements make assumptions about what kind of renderers they allow
    // as children so we can't allow author shadows on them for now. An override
    // flag is provided for testing how author shadows interact on these elements.
    if (!areAuthorShadowsAllowed() && !RuntimeEnabledFeatures::authorShadowDOMForAnyElementEnabled()) {
        exceptionState.throwDOMException(HierarchyRequestError, "Author-created shadow roots are disabled for this element.");
        return nullptr;
    }

    return PassRefPtr<ShadowRoot>(ensureShadow().addShadowRoot(*this, ShadowRoot::AuthorShadowRoot));
}

ShadowRoot* Element::shadowRoot() const
{
    ElementShadow* elementShadow = shadow();
    if (!elementShadow)
        return 0;
    ShadowRoot* shadowRoot = elementShadow->youngestShadowRoot();
    if (shadowRoot->type() == ShadowRoot::AuthorShadowRoot)
        return shadowRoot;
    return 0;
}

void Element::didAddShadowRoot(ShadowRoot&)
{
}

ShadowRoot* Element::userAgentShadowRoot() const
{
    if (ElementShadow* elementShadow = shadow()) {
        if (ShadowRoot* shadowRoot = elementShadow->oldestShadowRoot()) {
            ASSERT(shadowRoot->type() == ShadowRoot::UserAgentShadowRoot);
            return shadowRoot;
        }
    }

    return 0;
}

ShadowRoot& Element::ensureUserAgentShadowRoot()
{
    if (ShadowRoot* shadowRoot = userAgentShadowRoot())
        return *shadowRoot;
    ShadowRoot& shadowRoot = ensureShadow().addShadowRoot(*this, ShadowRoot::UserAgentShadowRoot);
    didAddUserAgentShadowRoot(shadowRoot);
    return shadowRoot;
}

bool Element::childTypeAllowed(NodeType type) const
{
    switch (type) {
    case ELEMENT_NODE:
    case TEXT_NODE:
    case COMMENT_NODE:
    case PROCESSING_INSTRUCTION_NODE:
    case CDATA_SECTION_NODE:
        return true;
    default:
        break;
    }
    return false;
}

void Element::checkForEmptyStyleChange(RenderStyle* style)
{
    if (!style && !styleAffectedByEmpty())
        return;

    if (!style || (styleAffectedByEmpty() && (!style->emptyState() || hasChildren())))
        setNeedsStyleRecalc(SubtreeStyleChange);
}

void Element::checkForSiblingStyleChanges(bool finishedParsingCallback, Node* beforeChange, Node* afterChange, int childCountDelta)
{
    if (!inActiveDocument() || document().hasPendingForcedStyleRecalc() || styleChangeType() >= SubtreeStyleChange)
        return;

    RenderStyle* style = renderStyle();

    // :empty selector.
    checkForEmptyStyleChange(style);

    if (!style || (needsStyleRecalc() && childrenAffectedByPositionalRules()))
        return;

    // Forward positional selectors include nth-child, nth-of-type, first-of-type and only-of-type.
    // The indirect adjacent selector is the ~ selector.
    // Backward positional selectors include nth-last-child, nth-last-of-type, last-of-type and only-of-type.
    // We have to invalidate everything following the insertion point in the forward and indirect adjacent case,
    // and everything before the insertion point in the backward case.
    // |afterChange| is 0 in the parser callback case, so we won't do any work for the forward case if we don't have to.
    // For performance reasons we just mark the parent node as changed, since we don't want to make childrenChanged O(n^2) by crawling all our kids
    // here. recalcStyle will then force a walk of the children when it sees that this has happened.
    if (((childrenAffectedByForwardPositionalRules() || childrenAffectedByIndirectAdjacentRules()) && afterChange)
        || (childrenAffectedByBackwardPositionalRules() && beforeChange)) {
        setNeedsStyleRecalc(SubtreeStyleChange);
        return;
    }

    // :first-child.  In the parser callback case, we don't have to check anything, since we were right the first time.
    // In the DOM case, we only need to do something if |afterChange| is not 0.
    // |afterChange| is 0 in the parser case, so it works out that we'll skip this block.
    if (childrenAffectedByFirstChildRules() && afterChange) {
        // Find our new first child.
        Element* newFirstChild = ElementTraversal::firstWithin(*this);
        RenderStyle* newFirstChildStyle = newFirstChild ? newFirstChild->renderStyle() : 0;

        // Find the first element node following |afterChange|
        Node* firstElementAfterInsertion = afterChange->isElementNode() ? afterChange : ElementTraversal::nextSibling(*afterChange);
        RenderStyle* firstElementAfterInsertionStyle = firstElementAfterInsertion ? firstElementAfterInsertion->renderStyle() : 0;

        // This is the insert/append case.
        if (newFirstChild != firstElementAfterInsertion && firstElementAfterInsertionStyle && firstElementAfterInsertionStyle->firstChildState())
            firstElementAfterInsertion->setNeedsStyleRecalc(SubtreeStyleChange);

        // We also have to handle node removal.
        if (childCountDelta < 0 && newFirstChild == firstElementAfterInsertion && newFirstChild && (!newFirstChildStyle || !newFirstChildStyle->firstChildState()))
            newFirstChild->setNeedsStyleRecalc(SubtreeStyleChange);
    }

    // :last-child.  In the parser callback case, we don't have to check anything, since we were right the first time.
    // In the DOM case, we only need to do something if |afterChange| is not 0.
    if (childrenAffectedByLastChildRules() && beforeChange) {
        // Find our new last child.
        Node* newLastChild = ElementTraversal::lastWithin(*this);
        RenderStyle* newLastChildStyle = newLastChild ? newLastChild->renderStyle() : 0;

        // Find the last element node going backwards from |beforeChange|
        Node* lastElementBeforeInsertion = beforeChange->isElementNode() ? beforeChange : ElementTraversal::previousSibling(*beforeChange);
        RenderStyle* lastElementBeforeInsertionStyle = lastElementBeforeInsertion ? lastElementBeforeInsertion->renderStyle() : 0;

        if (newLastChild != lastElementBeforeInsertion && lastElementBeforeInsertionStyle && lastElementBeforeInsertionStyle->lastChildState())
            lastElementBeforeInsertion->setNeedsStyleRecalc(SubtreeStyleChange);

        // We also have to handle node removal.  The parser callback case is similar to node removal as well in that we need to change the last child
        // to match now.
        if ((childCountDelta < 0 || finishedParsingCallback) && newLastChild == lastElementBeforeInsertion && newLastChild && (!newLastChildStyle || !newLastChildStyle->lastChildState()))
            newLastChild->setNeedsStyleRecalc(SubtreeStyleChange);
    }

    // The + selector.  We need to invalidate the first element following the insertion point.  It is the only possible element
    // that could be affected by this DOM change.
    if (childrenAffectedByDirectAdjacentRules() && afterChange) {
        if (Node* firstElementAfterInsertion = afterChange->isElementNode() ? afterChange : ElementTraversal::nextSibling(*afterChange))
            firstElementAfterInsertion->setNeedsStyleRecalc(SubtreeStyleChange);
    }
}

void Element::childrenChanged(bool changedByParser, Node* beforeChange, Node* afterChange, int childCountDelta)
{
    ContainerNode::childrenChanged(changedByParser, beforeChange, afterChange, childCountDelta);
    if (changedByParser)
        checkForEmptyStyleChange(renderStyle());
    else
        checkForSiblingStyleChanges(false, beforeChange, afterChange, childCountDelta);

    if (ElementShadow* shadow = this->shadow())
        shadow->setNeedsDistributionRecalc();
}

void Element::removeAllEventListeners()
{
    ContainerNode::removeAllEventListeners();
    if (ElementShadow* shadow = this->shadow())
        shadow->removeAllEventListeners();
}

void Element::finishParsingChildren()
{
    setIsFinishedParsingChildren(true);
    checkForSiblingStyleChanges(this, lastChild(), 0, 0);
}

#ifndef NDEBUG
void Element::formatForDebugger(char* buffer, unsigned length) const
{
    StringBuilder result;
    String s;

    result.append(nodeName());

    s = getIdAttribute();
    if (s.length() > 0) {
        if (result.length() > 0)
            result.appendLiteral("; ");
        result.appendLiteral("id=");
        result.append(s);
    }

    s = getAttribute(classAttr);
    if (s.length() > 0) {
        if (result.length() > 0)
            result.appendLiteral("; ");
        result.appendLiteral("class=");
        result.append(s);
    }

    strncpy(buffer, result.toString().utf8().data(), length - 1);
}
#endif

const Vector<RefPtr<Attr> >& Element::attrNodeList()
{
    ASSERT(hasSyntheticAttrChildNodes());
    return *attrNodeListForElement(this);
}

PassRefPtr<Attr> Element::setAttributeNode(Attr* attrNode, ExceptionState& exceptionState)
{
    if (!attrNode) {
        exceptionState.throwDOMException(TypeMismatchError, ExceptionMessages::argumentNullOrIncorrectType(1, "Attr"));
        return nullptr;
    }

    RefPtr<Attr> oldAttrNode = attrIfExists(attrNode->qualifiedName());
    if (oldAttrNode.get() == attrNode)
        return attrNode; // This Attr is already attached to the element.

    // InUseAttributeError: Raised if node is an Attr that is already an attribute of another Element object.
    // The DOM user must explicitly clone Attr nodes to re-use them in other elements.
    if (attrNode->ownerElement()) {
        exceptionState.throwDOMException(InUseAttributeError, "The node provided is an attribute node that is already an attribute of another Element; attribute nodes must be explicitly cloned.");
        return nullptr;
    }

    synchronizeAllAttributes();
    UniqueElementData& elementData = ensureUniqueElementData();

    size_t index = elementData.getAttributeItemIndex(attrNode->qualifiedName(), shouldIgnoreAttributeCase());
    if (index != kNotFound) {
        if (oldAttrNode)
            detachAttrNodeFromElementWithValue(oldAttrNode.get(), elementData.attributeItem(index).value());
        else
            oldAttrNode = Attr::create(document(), attrNode->qualifiedName(), elementData.attributeItem(index).value());
    }

    setAttributeInternal(index, attrNode->qualifiedName(), attrNode->value(), NotInSynchronizationOfLazyAttribute);

    attrNode->attachToElement(this);
    treeScope().adoptIfNeeded(*attrNode);
    ensureAttrNodeListForElement(this).append(attrNode);

    return oldAttrNode.release();
}

PassRefPtr<Attr> Element::removeAttributeNode(Attr* attr, ExceptionState& exceptionState)
{
    if (!attr) {
        exceptionState.throwDOMException(TypeMismatchError, ExceptionMessages::argumentNullOrIncorrectType(1, "Attr"));
        return nullptr;
    }
    if (attr->ownerElement() != this) {
        exceptionState.throwDOMException(NotFoundError, "The node provided is owned by another element.");
        return nullptr;
    }

    ASSERT(document() == attr->document());

    synchronizeAttribute(attr->qualifiedName());

    size_t index = elementData()->getAttrIndex(attr);
    if (index == kNotFound) {
        exceptionState.throwDOMException(NotFoundError, "The attribute was not found on this element.");
        return nullptr;
    }

    RefPtr<Attr> guard(attr);
    detachAttrNodeAtIndex(attr, index);
    return guard.release();
}

bool Element::parseAttributeName(QualifiedName& out, const AtomicString& namespaceURI, const AtomicString& qualifiedName, ExceptionState& exceptionState)
{
    AtomicString prefix, localName;
    if (!Document::parseQualifiedName(qualifiedName, prefix, localName, exceptionState))
        return false;
    ASSERT(!exceptionState.hadException());

    QualifiedName qName(prefix, localName, namespaceURI);

    if (!Document::hasValidNamespaceForAttributes(qName)) {
        exceptionState.throwDOMException(NamespaceError, "'" + namespaceURI + "' is an invalid namespace for attributes.");
        return false;
    }

    out = qName;
    return true;
}

void Element::setAttributeNS(const AtomicString& namespaceURI, const AtomicString& qualifiedName, const AtomicString& value, ExceptionState& exceptionState)
{
    QualifiedName parsedName = anyName;
    if (!parseAttributeName(parsedName, namespaceURI, qualifiedName, exceptionState))
        return;
    setAttribute(parsedName, value);
}

void Element::removeAttributeInternal(size_t index, SynchronizationOfLazyAttribute inSynchronizationOfLazyAttribute)
{
    ASSERT_WITH_SECURITY_IMPLICATION(index < attributeCount());

    UniqueElementData& elementData = ensureUniqueElementData();

    QualifiedName name = elementData.attributeItem(index).name();
    AtomicString valueBeingRemoved = elementData.attributeItem(index).value();

    if (!inSynchronizationOfLazyAttribute) {
        if (!valueBeingRemoved.isNull())
            willModifyAttribute(name, valueBeingRemoved, nullAtom);
    }

    if (RefPtr<Attr> attrNode = attrIfExists(name))
        detachAttrNodeFromElementWithValue(attrNode.get(), elementData.attributeItem(index).value());

    elementData.removeAttribute(index);

    if (!inSynchronizationOfLazyAttribute)
        didRemoveAttribute(name);
}

void Element::addAttributeInternal(const QualifiedName& name, const AtomicString& value, SynchronizationOfLazyAttribute inSynchronizationOfLazyAttribute)
{
    if (!inSynchronizationOfLazyAttribute)
        willModifyAttribute(name, nullAtom, value);
    ensureUniqueElementData().addAttribute(name, value);
    if (!inSynchronizationOfLazyAttribute)
        didAddAttribute(name, value);
}

void Element::removeAttribute(const AtomicString& name)
{
    if (!elementData())
        return;

    AtomicString localName = shouldIgnoreAttributeCase() ? name.lower() : name;
    size_t index = elementData()->getAttributeItemIndex(localName, false);
    if (index == kNotFound) {
        if (UNLIKELY(localName == styleAttr) && elementData()->m_styleAttributeIsDirty && isStyledElement())
            removeAllInlineStyleProperties();
        return;
    }

    removeAttributeInternal(index, NotInSynchronizationOfLazyAttribute);
}

void Element::removeAttributeNS(const AtomicString& namespaceURI, const AtomicString& localName)
{
    removeAttribute(QualifiedName(nullAtom, localName, namespaceURI));
}

PassRefPtr<Attr> Element::getAttributeNode(const AtomicString& localName)
{
    if (!elementData())
        return nullptr;
    synchronizeAttribute(localName);
    const Attribute* attribute = elementData()->getAttributeItem(localName, shouldIgnoreAttributeCase());
    if (!attribute)
        return nullptr;
    return ensureAttr(attribute->name());
}

PassRefPtr<Attr> Element::getAttributeNodeNS(const AtomicString& namespaceURI, const AtomicString& localName)
{
    if (!elementData())
        return nullptr;
    QualifiedName qName(nullAtom, localName, namespaceURI);
    synchronizeAttribute(qName);
    const Attribute* attribute = elementData()->getAttributeItem(qName);
    if (!attribute)
        return nullptr;
    return ensureAttr(attribute->name());
}

bool Element::hasAttribute(const AtomicString& localName) const
{
    if (!elementData())
        return false;
    synchronizeAttribute(localName);
    return elementData()->getAttributeItem(shouldIgnoreAttributeCase() ? localName.lower() : localName, false);
}

bool Element::hasAttributeNS(const AtomicString& namespaceURI, const AtomicString& localName) const
{
    if (!elementData())
        return false;
    QualifiedName qName(nullAtom, localName, namespaceURI);
    synchronizeAttribute(qName);
    return elementData()->getAttributeItem(qName);
}

void Element::focus(bool restorePreviousSelection, FocusType type)
{
    if (!inDocument())
        return;

    Document& doc = document();
    if (doc.focusedElement() == this)
        return;

    // If the stylesheets have already been loaded we can reliably check isFocusable.
    // If not, we continue and set the focused node on the focus controller below so
    // that it can be updated soon after attach.
    if (doc.haveStylesheetsLoaded()) {
        doc.updateLayoutIgnorePendingStylesheets();
        if (!isFocusable())
            return;
    }

    if (!supportsFocus())
        return;

    RefPtr<Node> protect;
    if (Page* page = doc.page()) {
        // Focus and change event handlers can cause us to lose our last ref.
        // If a focus event handler changes the focus to a different node it
        // does not make sense to continue and update appearence.
        protect = this;
        if (!page->focusController().setFocusedElement(this, doc.frame(), type))
            return;
    }

    // Setting the focused node above might have invalidated the layout due to scripts.
    doc.updateLayoutIgnorePendingStylesheets();

    if (!isFocusable()) {
        setElementFlag(NeedsFocusAppearanceUpdateSoonAfterAttach);
        return;
    }

    cancelFocusAppearanceUpdate();
    updateFocusAppearance(restorePreviousSelection);
}

void Element::updateFocusAppearance(bool /*restorePreviousSelection*/)
{
    if (isRootEditableElement()) {
        LocalFrame* frame = document().frame();
        if (!frame)
            return;

        // When focusing an editable element in an iframe, don't reset the selection if it already contains a selection.
        if (this == frame->selection().rootEditableElement())
            return;

        // FIXME: We should restore the previous selection if there is one.
        VisibleSelection newSelection = VisibleSelection(firstPositionInOrBeforeNode(this), DOWNSTREAM);
        frame->selection().setSelection(newSelection);
        frame->selection().revealSelection();
    } else if (renderer() && !renderer()->isWidget())
        renderer()->scrollRectToVisible(boundingBox());
}

void Element::blur()
{
    cancelFocusAppearanceUpdate();
    if (treeScope().adjustedFocusedElement() == this) {
        Document& doc = document();
        if (doc.page())
            doc.page()->focusController().setFocusedElement(0, doc.frame());
        else
            doc.setFocusedElement(nullptr);
    }
}

bool Element::isFocusable() const
{
    return inDocument() && supportsFocus() && !isInert() && rendererIsFocusable();
}

bool Element::isKeyboardFocusable() const
{
    return isFocusable() && tabIndex() >= 0;
}

bool Element::isMouseFocusable() const
{
    return isFocusable();
}

void Element::dispatchFocusEvent(Element* oldFocusedElement, FocusType)
{
    RefPtrWillBeRawPtr<FocusEvent> event = FocusEvent::create(EventTypeNames::focus, false, false, document().domWindow(), 0, oldFocusedElement);
    EventDispatcher::dispatchEvent(this, FocusEventDispatchMediator::create(event.release()));
}

void Element::dispatchBlurEvent(Element* newFocusedElement)
{
    RefPtrWillBeRawPtr<FocusEvent> event = FocusEvent::create(EventTypeNames::blur, false, false, document().domWindow(), 0, newFocusedElement);
    EventDispatcher::dispatchEvent(this, BlurEventDispatchMediator::create(event.release()));
}

void Element::dispatchFocusInEvent(const AtomicString& eventType, Element* oldFocusedElement)
{
    ASSERT(!NoEventDispatchAssertion::isEventDispatchForbidden());
    ASSERT(eventType == EventTypeNames::focusin || eventType == EventTypeNames::DOMFocusIn);
    dispatchScopedEventDispatchMediator(FocusInEventDispatchMediator::create(FocusEvent::create(eventType, true, false, document().domWindow(), 0, oldFocusedElement)));
}

void Element::dispatchFocusOutEvent(const AtomicString& eventType, Element* newFocusedElement)
{
    ASSERT(!NoEventDispatchAssertion::isEventDispatchForbidden());
    ASSERT(eventType == EventTypeNames::focusout || eventType == EventTypeNames::DOMFocusOut);
    dispatchScopedEventDispatchMediator(FocusOutEventDispatchMediator::create(FocusEvent::create(eventType, true, false, document().domWindow(), 0, newFocusedElement)));
}

String Element::innerHTML() const
{
    return createMarkup(this, ChildrenOnly);
}

String Element::outerHTML() const
{
    return createMarkup(this);
}

void Element::setInnerHTML(const String& html, ExceptionState& exceptionState)
{
    if (RefPtr<DocumentFragment> fragment = createFragmentForInnerOuterHTML(html, this, AllowScriptingContent, "innerHTML", exceptionState)) {
        ContainerNode* container = this;
        if (isHTMLTemplateElement(*this))
            container = toHTMLTemplateElement(this)->content();
        replaceChildrenWithFragment(container, fragment.release(), exceptionState);
    }
}

void Element::setOuterHTML(const String& html, ExceptionState& exceptionState)
{
    Node* p = parentNode();
    if (!p) {
        exceptionState.throwDOMException(NoModificationAllowedError, "This element has no parent node.");
        return;
    }
    if (!p->isElementNode()) {
        exceptionState.throwDOMException(NoModificationAllowedError, "This element's parent is of type '" + p->nodeName() + "', which is not an element node.");
        return;
    }

    RefPtr<Element> parent = toElement(p);
    RefPtr<Node> prev = previousSibling();
    RefPtr<Node> next = nextSibling();

    RefPtr<DocumentFragment> fragment = createFragmentForInnerOuterHTML(html, parent.get(), AllowScriptingContent, "outerHTML", exceptionState);
    if (exceptionState.hadException())
        return;

    parent->replaceChild(fragment.release(), this, exceptionState);
    RefPtr<Node> node = next ? next->previousSibling() : 0;
    if (!exceptionState.hadException() && node && node->isTextNode())
        mergeWithNextTextNode(node.release(), exceptionState);

    if (!exceptionState.hadException() && prev && prev->isTextNode())
        mergeWithNextTextNode(prev.release(), exceptionState);
}

Node* Element::insertAdjacent(const String& where, Node* newChild, ExceptionState& exceptionState)
{
    if (equalIgnoringCase(where, "beforeBegin")) {
        if (ContainerNode* parent = this->parentNode()) {
            parent->insertBefore(newChild, this, exceptionState);
            if (!exceptionState.hadException())
                return newChild;
        }
        return 0;
    }

    if (equalIgnoringCase(where, "afterBegin")) {
        insertBefore(newChild, firstChild(), exceptionState);
        return exceptionState.hadException() ? 0 : newChild;
    }

    if (equalIgnoringCase(where, "beforeEnd")) {
        appendChild(newChild, exceptionState);
        return exceptionState.hadException() ? 0 : newChild;
    }

    if (equalIgnoringCase(where, "afterEnd")) {
        if (ContainerNode* parent = this->parentNode()) {
            parent->insertBefore(newChild, nextSibling(), exceptionState);
            if (!exceptionState.hadException())
                return newChild;
        }
        return 0;
    }

    exceptionState.throwDOMException(SyntaxError, "The value provided ('" + where + "') is not one of 'beforeBegin', 'afterBegin', 'beforeEnd', or 'afterEnd'.");
    return 0;
}

// Step 1 of http://domparsing.spec.whatwg.org/#insertadjacenthtml()
static Element* contextElementForInsertion(const String& where, Element* element, ExceptionState& exceptionState)
{
    if (equalIgnoringCase(where, "beforeBegin") || equalIgnoringCase(where, "afterEnd")) {
        ContainerNode* parent = element->parentNode();
        if (!parent || !parent->isElementNode()) {
            exceptionState.throwDOMException(NoModificationAllowedError, "The element has no parent.");
            return 0;
        }
        return toElement(parent);
    }
    if (equalIgnoringCase(where, "afterBegin") || equalIgnoringCase(where, "beforeEnd"))
        return element;
    exceptionState.throwDOMException(SyntaxError, "The value provided ('" + where + "') is not one of 'beforeBegin', 'afterBegin', 'beforeEnd', or 'afterEnd'.");
    return 0;
}

Element* Element::insertAdjacentElement(const String& where, Element* newChild, ExceptionState& exceptionState)
{
    if (!newChild) {
        // IE throws COM Exception E_INVALIDARG; this is the best DOM exception alternative.
        exceptionState.throwTypeError("The node provided is null.");
        return 0;
    }

    Node* returnValue = insertAdjacent(where, newChild, exceptionState);
    return toElement(returnValue);
}

void Element::insertAdjacentText(const String& where, const String& text, ExceptionState& exceptionState)
{
    RefPtr<Text> textNode = document().createTextNode(text);
    insertAdjacent(where, textNode.get(), exceptionState);
}

void Element::insertAdjacentHTML(const String& where, const String& markup, ExceptionState& exceptionState)
{
    RefPtr<Element> contextElement = contextElementForInsertion(where, this, exceptionState);
    if (!contextElement)
        return;

    RefPtr<DocumentFragment> fragment = createFragmentForInnerOuterHTML(markup, contextElement.get(), AllowScriptingContent, "insertAdjacentHTML", exceptionState);
    if (!fragment)
        return;
    insertAdjacent(where, fragment.get(), exceptionState);
}

String Element::innerText()
{
    // We need to update layout, since plainText uses line boxes in the render tree.
    document().updateLayoutIgnorePendingStylesheets();

    if (!renderer())
        return textContent(true);

    return plainText(rangeOfContents(const_cast<Element*>(this)).get());
}

String Element::outerText()
{
    // Getting outerText is the same as getting innerText, only
    // setting is different. You would think this should get the plain
    // text for the outer range, but this is wrong, <br> for instance
    // would return different values for inner and outer text by such
    // a rule, but it doesn't in WinIE, and we want to match that.
    return innerText();
}

String Element::textFromChildren()
{
    Text* firstTextNode = 0;
    bool foundMultipleTextNodes = false;
    unsigned totalLength = 0;

    for (Node* child = firstChild(); child; child = child->nextSibling()) {
        if (!child->isTextNode())
            continue;
        Text* text = toText(child);
        if (!firstTextNode)
            firstTextNode = text;
        else
            foundMultipleTextNodes = true;
        unsigned length = text->data().length();
        if (length > std::numeric_limits<unsigned>::max() - totalLength)
            return emptyString();
        totalLength += length;
    }

    if (!firstTextNode)
        return emptyString();

    if (firstTextNode && !foundMultipleTextNodes) {
        firstTextNode->atomize();
        return firstTextNode->data();
    }

    StringBuilder content;
    content.reserveCapacity(totalLength);
    for (Node* child = firstTextNode; child; child = child->nextSibling()) {
        if (!child->isTextNode())
            continue;
        content.append(toText(child)->data());
    }

    ASSERT(content.length() == totalLength);
    return content.toString();
}

const AtomicString& Element::shadowPseudoId() const
{
    if (ShadowRoot* root = containingShadowRoot()) {
        if (root->type() == ShadowRoot::UserAgentShadowRoot)
            return fastGetAttribute(pseudoAttr);
    }
    return nullAtom;
}

void Element::setShadowPseudoId(const AtomicString& id)
{
    ASSERT(CSSSelector::parsePseudoType(id) == CSSSelector::PseudoWebKitCustomElement || CSSSelector::parsePseudoType(id) == CSSSelector::PseudoUserAgentCustomElement);
    setAttribute(pseudoAttr, id);
}

bool Element::isInDescendantTreeOf(const Element* shadowHost) const
{
    ASSERT(shadowHost);
    ASSERT(isShadowHost(shadowHost));

    const ShadowRoot* shadowRoot = containingShadowRoot();
    while (shadowRoot) {
        const Element* ancestorShadowHost = shadowRoot->shadowHost();
        if (ancestorShadowHost == shadowHost)
            return true;
        shadowRoot = ancestorShadowHost->containingShadowRoot();
    }
    return false;
}

LayoutSize Element::minimumSizeForResizing() const
{
    return hasRareData() ? elementRareData()->minimumSizeForResizing() : defaultMinimumSizeForResizing();
}

void Element::setMinimumSizeForResizing(const LayoutSize& size)
{
    if (!hasRareData() && size == defaultMinimumSizeForResizing())
        return;
    ensureElementRareData().setMinimumSizeForResizing(size);
}

RenderStyle* Element::computedStyle(PseudoId pseudoElementSpecifier)
{
    if (PseudoElement* element = pseudoElement(pseudoElementSpecifier))
        return element->computedStyle();

    // FIXME: Find and use the renderer from the pseudo element instead of the actual element so that the 'length'
    // properties, which are only known by the renderer because it did the layout, will be correct and so that the
    // values returned for the ":selection" pseudo-element will be correct.
    if (RenderStyle* usedStyle = renderStyle()) {
        if (pseudoElementSpecifier) {
            RenderStyle* cachedPseudoStyle = usedStyle->getCachedPseudoStyle(pseudoElementSpecifier);
            return cachedPseudoStyle ? cachedPseudoStyle : usedStyle;
         } else
            return usedStyle;
    }

    if (!inActiveDocument())
        // FIXME: Try to do better than this. Ensure that styleForElement() works for elements that are not in the
        // document tree and figure out when to destroy the computed style for such elements.
        return 0;

    ElementRareData& rareData = ensureElementRareData();
    if (!rareData.computedStyle())
        rareData.setComputedStyle(document().styleForElementIgnoringPendingStylesheets(this));
    return pseudoElementSpecifier ? rareData.computedStyle()->getCachedPseudoStyle(pseudoElementSpecifier) : rareData.computedStyle();
}

void Element::setChildIndex(unsigned index)
{
    ElementRareData& rareData = ensureElementRareData();
    if (RenderStyle* style = renderStyle())
        style->setUnique();
    rareData.setChildIndex(index);
}

unsigned Element::rareDataChildIndex() const
{
    ASSERT(hasRareData());
    return elementRareData()->childIndex();
}

AtomicString Element::computeInheritedLanguage() const
{
    const Node* n = this;
    AtomicString value;
    // The language property is inherited, so we iterate over the parents to find the first language.
    do {
        if (n->isElementNode()) {
            if (const ElementData* elementData = toElement(n)->elementData()) {
                // Spec: xml:lang takes precedence -- http://www.w3.org/TR/xhtml1/#C_7
                if (const Attribute* attribute = elementData->getAttributeItem(XMLNames::langAttr))
                    value = attribute->value();
                else if (const Attribute* attribute = elementData->getAttributeItem(HTMLNames::langAttr))
                    value = attribute->value();
            }
        } else if (n->isDocumentNode()) {
            // checking the MIME content-language
            value = toDocument(n)->contentLanguage();
        }

        n = n->parentNode();
    } while (n && value.isNull());

    return value;
}

Locale& Element::locale() const
{
    return document().getCachedLocale(computeInheritedLanguage());
}

void Element::cancelFocusAppearanceUpdate()
{
    if (hasRareData())
        clearElementFlag(NeedsFocusAppearanceUpdateSoonAfterAttach);
    if (document().focusedElement() == this)
        document().cancelFocusAppearanceUpdate();
}

void Element::normalizeAttributes()
{
    if (!hasAttributes())
        return;
    // attributeCount() cannot be cached before the loop because the attributes
    // list is altered while iterating.
    for (unsigned i = 0; i < attributeCount(); ++i) {
        if (RefPtr<Attr> attr = attrIfExists(attributeItem(i).name()))
            attr->normalize();
    }
}

void Element::updatePseudoElement(PseudoId pseudoId, StyleRecalcChange change)
{
    ASSERT(!needsStyleRecalc());
    PseudoElement* element = pseudoElement(pseudoId);
    if (element && (change == UpdatePseudoElements || element->shouldCallRecalcStyle(change))) {

        // Need to clear the cached style if the PseudoElement wants a recalc so it
        // computes a new style.
        if (element->needsStyleRecalc())
            renderer()->style()->removeCachedPseudoStyle(pseudoId);

        // PseudoElement styles hang off their parent element's style so if we needed
        // a style recalc we should Force one on the pseudo.
        // FIXME: We should figure out the right text sibling to pass.
        element->recalcStyle(change == UpdatePseudoElements ? Force : change);

        // Wait until our parent is not displayed or pseudoElementRendererIsNeeded
        // is false, otherwise we could continously create and destroy PseudoElements
        // when RenderObject::isChildAllowed on our parent returns false for the
        // PseudoElement's renderer for each style recalc.
        if (!renderer() || !pseudoElementRendererIsNeeded(renderer()->getCachedPseudoStyle(pseudoId)))
            elementRareData()->setPseudoElement(pseudoId, nullptr);
    } else if (change >= UpdatePseudoElements) {
        createPseudoElementIfNeeded(pseudoId);
    }
}

void Element::createPseudoElementIfNeeded(PseudoId pseudoId)
{
    if (isPseudoElement())
        return;

    // Document::ensureStyleResolver is not inlined and shows up on profiles, avoid it here.
    StyleEngine* engine = document().styleEngine();
    RefPtr<PseudoElement> element = engine->ensureResolver().createPseudoElementIfNeeded(*this, pseudoId);
    if (!element)
        return;

    if (pseudoId == BACKDROP)
        document().addToTopLayer(element.get(), this);
    element->insertedInto(this);
    element->attach();

    InspectorInstrumentation::pseudoElementCreated(element.get());

    ensureElementRareData().setPseudoElement(pseudoId, element.release());
}

PseudoElement* Element::pseudoElement(PseudoId pseudoId) const
{
    return hasRareData() ? elementRareData()->pseudoElement(pseudoId) : 0;
}

RenderObject* Element::pseudoElementRenderer(PseudoId pseudoId) const
{
    if (PseudoElement* element = pseudoElement(pseudoId))
        return element->renderer();
    return 0;
}

bool Element::matches(const String& selectors, ExceptionState& exceptionState)
{
    SelectorQuery* selectorQuery = document().selectorQueryCache().add(AtomicString(selectors), document(), exceptionState);
    if (!selectorQuery)
        return false;
    return selectorQuery->matches(*this);
}

DOMTokenList& Element::classList()
{
    ElementRareData& rareData = ensureElementRareData();
    if (!rareData.classList())
        rareData.setClassList(ClassList::create(this));
    return *rareData.classList();
}

DOMStringMap& Element::dataset()
{
    ElementRareData& rareData = ensureElementRareData();
    if (!rareData.dataset())
        rareData.setDataset(DatasetDOMStringMap::create(this));
    return *rareData.dataset();
}

KURL Element::getURLAttribute(const QualifiedName& name) const
{
#if !ASSERT_DISABLED
    if (elementData()) {
        if (const Attribute* attribute = getAttributeItem(name))
            ASSERT(isURLAttribute(*attribute));
    }
#endif
    return document().completeURL(stripLeadingAndTrailingHTMLSpaces(getAttribute(name)));
}

KURL Element::getNonEmptyURLAttribute(const QualifiedName& name) const
{
#if !ASSERT_DISABLED
    if (elementData()) {
        if (const Attribute* attribute = getAttributeItem(name))
            ASSERT(isURLAttribute(*attribute));
    }
#endif
    String value = stripLeadingAndTrailingHTMLSpaces(getAttribute(name));
    if (value.isEmpty())
        return KURL();
    return document().completeURL(value);
}

int Element::getIntegralAttribute(const QualifiedName& attributeName) const
{
    return getAttribute(attributeName).string().toInt();
}

void Element::setIntegralAttribute(const QualifiedName& attributeName, int value)
{
    setAttribute(attributeName, AtomicString::number(value));
}

unsigned Element::getUnsignedIntegralAttribute(const QualifiedName& attributeName) const
{
    return getAttribute(attributeName).string().toUInt();
}

void Element::setUnsignedIntegralAttribute(const QualifiedName& attributeName, unsigned value)
{
    // Range restrictions are enforced for unsigned IDL attributes that
    // reflect content attributes,
    //   http://www.whatwg.org/specs/web-apps/current-work/multipage/common-dom-interfaces.html#reflecting-content-attributes-in-idl-attributes
    if (value > 0x7fffffffu)
        value = 0;
    setAttribute(attributeName, AtomicString::number(value));
}

double Element::getFloatingPointAttribute(const QualifiedName& attributeName, double fallbackValue) const
{
    return parseToDoubleForNumberType(getAttribute(attributeName), fallbackValue);
}

void Element::setFloatingPointAttribute(const QualifiedName& attributeName, double value)
{
    setAttribute(attributeName, AtomicString::number(value));
}

void Element::webkitRequestFullscreen()
{
    FullscreenElementStack::from(document()).requestFullScreenForElement(this, ALLOW_KEYBOARD_INPUT, FullscreenElementStack::EnforceIFrameAllowFullScreenRequirement);
}

void Element::webkitRequestFullScreen(unsigned short flags)
{
    FullscreenElementStack::from(document()).requestFullScreenForElement(this, (flags | LEGACY_MOZILLA_REQUEST), FullscreenElementStack::EnforceIFrameAllowFullScreenRequirement);
}

void Element::setContainsFullScreenElement(bool flag)
{
    setElementFlag(ContainsFullScreenElement, flag);
    setNeedsStyleRecalc(SubtreeStyleChange);
}

static Element* parentCrossingFrameBoundaries(Element* element)
{
    ASSERT(element);
    return element->parentElement() ? element->parentElement() : element->document().ownerElement();
}

void Element::setContainsFullScreenElementOnAncestorsCrossingFrameBoundaries(bool flag)
{
    Element* element = this;
    while ((element = parentCrossingFrameBoundaries(element)))
        element->setContainsFullScreenElement(flag);
}

void Element::setIsInTopLayer(bool inTopLayer)
{
    if (isInTopLayer() == inTopLayer)
        return;
    setElementFlag(IsInTopLayer, inTopLayer);

    // We must ensure a reattach occurs so the renderer is inserted in the correct sibling order under RenderView according to its
    // top layer position, or in its usual place if not in the top layer.
    lazyReattachIfAttached();
}

void Element::webkitRequestPointerLock()
{
    if (document().page())
        document().page()->pointerLockController().requestPointerLock(this);
}

SpellcheckAttributeState Element::spellcheckAttributeState() const
{
    const AtomicString& value = fastGetAttribute(spellcheckAttr);
    if (value == nullAtom)
        return SpellcheckAttributeDefault;
    if (equalIgnoringCase(value, "true") || equalIgnoringCase(value, ""))
        return SpellcheckAttributeTrue;
    if (equalIgnoringCase(value, "false"))
        return SpellcheckAttributeFalse;

    return SpellcheckAttributeDefault;
}

bool Element::isSpellCheckingEnabled() const
{
    for (const Element* element = this; element; element = element->parentOrShadowHostElement()) {
        switch (element->spellcheckAttributeState()) {
        case SpellcheckAttributeTrue:
            return true;
        case SpellcheckAttributeFalse:
            return false;
        case SpellcheckAttributeDefault:
            break;
        }
    }

    return true;
}

#ifndef NDEBUG
bool Element::fastAttributeLookupAllowed(const QualifiedName& name) const
{
    if (name == HTMLNames::styleAttr)
        return false;

    if (isSVGElement())
        return !toSVGElement(this)->isAnimatableAttribute(name);

    return true;
}
#endif

#ifdef DUMP_NODE_STATISTICS
bool Element::hasNamedNodeMap() const
{
    return hasRareData() && elementRareData()->attributeMap();
}
#endif

inline void Element::updateName(const AtomicString& oldName, const AtomicString& newName)
{
    if (!inDocument() || isInShadowTree())
        return;

    if (oldName == newName)
        return;

    if (shouldRegisterAsNamedItem())
        updateNamedItemRegistration(oldName, newName);
}

inline void Element::updateId(const AtomicString& oldId, const AtomicString& newId)
{
    if (!isInTreeScope())
        return;

    if (oldId == newId)
        return;

    updateId(treeScope(), oldId, newId);
}

inline void Element::updateId(TreeScope& scope, const AtomicString& oldId, const AtomicString& newId)
{
    ASSERT(isInTreeScope());
    ASSERT(oldId != newId);

    if (!oldId.isEmpty())
        scope.removeElementById(oldId, this);
    if (!newId.isEmpty())
        scope.addElementById(newId, this);

    if (shouldRegisterAsExtraNamedItem())
        updateExtraNamedItemRegistration(oldId, newId);
}

void Element::updateLabel(TreeScope& scope, const AtomicString& oldForAttributeValue, const AtomicString& newForAttributeValue)
{
    ASSERT(isHTMLLabelElement(this));

    if (!inDocument())
        return;

    if (oldForAttributeValue == newForAttributeValue)
        return;

    if (!oldForAttributeValue.isEmpty())
        scope.removeLabel(oldForAttributeValue, toHTMLLabelElement(this));
    if (!newForAttributeValue.isEmpty())
        scope.addLabel(newForAttributeValue, toHTMLLabelElement(this));
}

void Element::willModifyAttribute(const QualifiedName& name, const AtomicString& oldValue, const AtomicString& newValue)
{
    if (isIdAttributeName(name)) {
        updateId(oldValue, newValue);
    } else if (name == HTMLNames::nameAttr) {
        updateName(oldValue, newValue);
    } else if (name == HTMLNames::forAttr && isHTMLLabelElement(*this)) {
        TreeScope& scope = treeScope();
        if (scope.shouldCacheLabelsByForAttribute())
            updateLabel(scope, oldValue, newValue);
    }

    if (oldValue != newValue) {
        if (inActiveDocument())
            document().ensureStyleResolver().ensureUpdatedRuleFeatureSet().scheduleStyleInvalidationForAttributeChange(name, *this);

        if (isUpgradedCustomElement())
            CustomElement::attributeDidChange(this, name.localName(), oldValue, newValue);
    }

    if (OwnPtr<MutationObserverInterestGroup> recipients = MutationObserverInterestGroup::createForAttributesMutation(*this, name))
        recipients->enqueueMutationRecord(MutationRecord::createAttributes(this, name, oldValue));

    InspectorInstrumentation::willModifyDOMAttr(this, oldValue, newValue);
}

void Element::didAddAttribute(const QualifiedName& name, const AtomicString& value)
{
    attributeChanged(name, value);
    InspectorInstrumentation::didModifyDOMAttr(this, name.localName(), value);
    dispatchSubtreeModifiedEvent();
}

void Element::didModifyAttribute(const QualifiedName& name, const AtomicString& value)
{
    attributeChanged(name, value);
    InspectorInstrumentation::didModifyDOMAttr(this, name.localName(), value);
    // Do not dispatch a DOMSubtreeModified event here; see bug 81141.
}

void Element::didRemoveAttribute(const QualifiedName& name)
{
    attributeChanged(name, nullAtom);
    InspectorInstrumentation::didRemoveDOMAttr(this, name.localName());
    dispatchSubtreeModifiedEvent();
}

static bool needsURLResolutionForInlineStyle(const Element& element, const Document& oldDocument, const Document& newDocument)
{
    if (oldDocument == newDocument)
        return false;
    if (oldDocument.baseURL() == newDocument.baseURL())
        return false;
    const StylePropertySet* style = element.inlineStyle();
    if (!style)
        return false;
    for (unsigned i = 0; i < style->propertyCount(); ++i) {
        // FIXME: Should handle all URL-based properties: CSSImageSetValue, CSSCursorImageValue, etc.
        if (style->propertyAt(i).value()->isImageValue())
            return true;
    }
    return false;
}

static void reResolveURLsInInlineStyle(const Document& document, MutableStylePropertySet& style)
{
    for (unsigned i = 0; i < style.propertyCount(); ++i) {
        StylePropertySet::PropertyReference property = style.propertyAt(i);
        // FIXME: Should handle all URL-based properties: CSSImageSetValue, CSSCursorImageValue, etc.
        if (property.value()->isImageValue())
            toCSSImageValue(property.value())->reResolveURL(document);
    }
}

void Element::didMoveToNewDocument(Document& oldDocument)
{
    Node::didMoveToNewDocument(oldDocument);

    // If the documents differ by quirks mode then they differ by case sensitivity
    // for class and id names so we need to go through the attribute change logic
    // to pick up the new casing in the ElementData.
    if (oldDocument.inQuirksMode() != document().inQuirksMode()) {
        if (hasID())
            setIdAttribute(getIdAttribute());
        if (hasClass())
            setAttribute(HTMLNames::classAttr, getClassAttribute());
    }

    if (needsURLResolutionForInlineStyle(*this, oldDocument, document()))
        reResolveURLsInInlineStyle(document(), ensureMutableInlineStyle());
}

void Element::updateNamedItemRegistration(const AtomicString& oldName, const AtomicString& newName)
{
    if (!document().isHTMLDocument())
        return;

    if (!oldName.isEmpty())
        toHTMLDocument(document()).removeNamedItem(oldName);

    if (!newName.isEmpty())
        toHTMLDocument(document()).addNamedItem(newName);
}

void Element::updateExtraNamedItemRegistration(const AtomicString& oldId, const AtomicString& newId)
{
    if (!document().isHTMLDocument())
        return;

    if (!oldId.isEmpty())
        toHTMLDocument(document()).removeExtraNamedItem(oldId);

    if (!newId.isEmpty())
        toHTMLDocument(document()).addExtraNamedItem(newId);
}

PassRefPtr<HTMLCollection> Element::ensureCachedHTMLCollection(CollectionType type)
{
    if (HTMLCollection* collection = cachedHTMLCollection(type))
        return collection;

    if (type == TableRows) {
        ASSERT(isHTMLTableElement(this));
        return ensureRareData().ensureNodeLists().addCache<HTMLTableRowsCollection>(*this, type);
    } else if (type == SelectOptions) {
        ASSERT(isHTMLSelectElement(this));
        return ensureRareData().ensureNodeLists().addCache<HTMLOptionsCollection>(*this, type);
    } else if (type == FormControls) {
        ASSERT(isHTMLFormElement(this) || isHTMLFieldSetElement(this));
        return ensureRareData().ensureNodeLists().addCache<HTMLFormControlsCollection>(*this, type);
    }
    return ensureRareData().ensureNodeLists().addCache<HTMLCollection>(*this, type);
}

void Element::scheduleLayerUpdate()
{
    document().scheduleLayerUpdate(*this);
}

HTMLCollection* Element::cachedHTMLCollection(CollectionType type)
{
    return hasRareData() && rareData()->nodeLists() ? rareData()->nodeLists()->cached<HTMLCollection>(type) : 0;
}

IntSize Element::savedLayerScrollOffset() const
{
    return hasRareData() ? elementRareData()->savedLayerScrollOffset() : IntSize();
}

void Element::setSavedLayerScrollOffset(const IntSize& size)
{
    if (size.isZero() && !hasRareData())
        return;
    ensureElementRareData().setSavedLayerScrollOffset(size);
}

PassRefPtr<Attr> Element::attrIfExists(const QualifiedName& name)
{
    if (AttrNodeList* attrNodeList = attrNodeListForElement(this))
        return findAttrNodeInList(*attrNodeList, name);
    return nullptr;
}

PassRefPtr<Attr> Element::ensureAttr(const QualifiedName& name)
{
    AttrNodeList& attrNodeList = ensureAttrNodeListForElement(this);
    RefPtr<Attr> attrNode = findAttrNodeInList(attrNodeList, name);
    if (!attrNode) {
        attrNode = Attr::create(*this, name);
        treeScope().adoptIfNeeded(*attrNode);
        attrNodeList.append(attrNode);
    }
    return attrNode.release();
}

void Element::detachAttrNodeFromElementWithValue(Attr* attrNode, const AtomicString& value)
{
    ASSERT(hasSyntheticAttrChildNodes());
    attrNode->detachFromElementWithValue(value);

    AttrNodeList* attrNodeList = attrNodeListForElement(this);
    for (unsigned i = 0; i < attrNodeList->size(); ++i) {
        if (attrNodeList->at(i)->qualifiedName() == attrNode->qualifiedName()) {
            attrNodeList->remove(i);
            if (attrNodeList->isEmpty())
                removeAttrNodeListForElement(this);
            return;
        }
    }
    ASSERT_NOT_REACHED();
}

void Element::detachAllAttrNodesFromElement()
{
    AttrNodeList* attrNodeList = attrNodeListForElement(this);
    ASSERT(attrNodeList);

    unsigned attributeCount = this->attributeCount();
    for (unsigned i = 0; i < attributeCount; ++i) {
        const Attribute& attribute = attributeItem(i);
        if (RefPtr<Attr> attrNode = findAttrNodeInList(*attrNodeList, attribute.name()))
            attrNode->detachFromElementWithValue(attribute.value());
    }

    removeAttrNodeListForElement(this);
}

void Element::willRecalcStyle(StyleRecalcChange)
{
    ASSERT(hasCustomStyleCallbacks());
}

void Element::didRecalcStyle(StyleRecalcChange)
{
    ASSERT(hasCustomStyleCallbacks());
}


PassRefPtr<RenderStyle> Element::customStyleForRenderer()
{
    ASSERT(hasCustomStyleCallbacks());
    return nullptr;
}

void Element::cloneAttributesFromElement(const Element& other)
{
    if (hasSyntheticAttrChildNodes())
        detachAllAttrNodesFromElement();

    other.synchronizeAllAttributes();
    if (!other.m_elementData) {
        m_elementData.clear();
        return;
    }

    const AtomicString& oldID = getIdAttribute();
    const AtomicString& newID = other.getIdAttribute();

    if (!oldID.isNull() || !newID.isNull())
        updateId(oldID, newID);

    const AtomicString& oldName = getNameAttribute();
    const AtomicString& newName = other.getNameAttribute();

    if (!oldName.isNull() || !newName.isNull())
        updateName(oldName, newName);

    // Quirks mode makes class and id not case sensitive. We can't share the ElementData
    // if the idForStyleResolution and the className need different casing.
    bool ownerDocumentsHaveDifferentCaseSensitivity = false;
    if (other.hasClass() || other.hasID())
        ownerDocumentsHaveDifferentCaseSensitivity = other.document().inQuirksMode() != document().inQuirksMode();

    // If 'other' has a mutable ElementData, convert it to an immutable one so we can share it between both elements.
    // We can only do this if there are no presentation attributes and sharing the data won't result in different case sensitivity of class or id.
    if (other.m_elementData->isUnique()
        && !ownerDocumentsHaveDifferentCaseSensitivity
        && !other.m_elementData->presentationAttributeStyle())
        const_cast<Element&>(other).m_elementData = static_cast<const UniqueElementData*>(other.m_elementData.get())->makeShareableCopy();

    if (!other.m_elementData->isUnique() && !ownerDocumentsHaveDifferentCaseSensitivity && !needsURLResolutionForInlineStyle(other, other.document(), document()))
        m_elementData = other.m_elementData;
    else
        m_elementData = other.m_elementData->makeUniqueCopy();

    unsigned length = m_elementData->length();
    for (unsigned i = 0; i < length; ++i) {
        const Attribute& attribute = m_elementData->attributeItem(i);
        attributeChangedFromParserOrByCloning(attribute.name(), attribute.value(), ModifiedByCloning);
    }
}

void Element::cloneDataFromElement(const Element& other)
{
    cloneAttributesFromElement(other);
    copyNonAttributePropertiesFromElement(other);
}

void Element::createUniqueElementData()
{
    if (!m_elementData)
        m_elementData = UniqueElementData::create();
    else {
        ASSERT(!m_elementData->isUnique());
        m_elementData = static_cast<ShareableElementData*>(m_elementData.get())->makeUniqueCopy();
    }
}

InputMethodContext& Element::inputMethodContext()
{
    return ensureElementRareData().ensureInputMethodContext(toHTMLElement(this));
}

bool Element::hasInputMethodContext() const
{
    return hasRareData() && elementRareData()->hasInputMethodContext();
}

void Element::synchronizeStyleAttributeInternal() const
{
    ASSERT(isStyledElement());
    ASSERT(elementData());
    ASSERT(elementData()->m_styleAttributeIsDirty);
    elementData()->m_styleAttributeIsDirty = false;
    const StylePropertySet* inlineStyle = this->inlineStyle();
    const_cast<Element*>(this)->setSynchronizedLazyAttribute(styleAttr,
        inlineStyle ? AtomicString(inlineStyle->asText()) : nullAtom);
}

CSSStyleDeclaration* Element::style()
{
    if (!isStyledElement())
        return 0;
    return &ensureElementRareData().ensureInlineCSSStyleDeclaration(this);
}

MutableStylePropertySet& Element::ensureMutableInlineStyle()
{
    ASSERT(isStyledElement());
    RefPtr<StylePropertySet>& inlineStyle = ensureUniqueElementData().m_inlineStyle;
    if (!inlineStyle) {
        CSSParserMode mode = (!isHTMLElement() || document().inQuirksMode()) ? HTMLQuirksMode : HTMLStandardMode;
        inlineStyle = MutableStylePropertySet::create(mode);
    } else if (!inlineStyle->isMutable()) {
        inlineStyle = inlineStyle->mutableCopy();
    }
    return *toMutableStylePropertySet(inlineStyle);
}

void Element::clearMutableInlineStyleIfEmpty()
{
    if (ensureMutableInlineStyle().isEmpty()) {
        ensureUniqueElementData().m_inlineStyle.clear();
    }
}

inline void Element::setInlineStyleFromString(const AtomicString& newStyleString)
{
    ASSERT(isStyledElement());
    RefPtr<StylePropertySet>& inlineStyle = elementData()->m_inlineStyle;

    // Avoid redundant work if we're using shared attribute data with already parsed inline style.
    if (inlineStyle && !elementData()->isUnique())
        return;

    // We reconstruct the property set instead of mutating if there is no CSSOM wrapper.
    // This makes wrapperless property sets immutable and so cacheable.
    if (inlineStyle && !inlineStyle->isMutable())
        inlineStyle.clear();

    if (!inlineStyle) {
        inlineStyle = BisonCSSParser::parseInlineStyleDeclaration(newStyleString, this);
    } else {
        ASSERT(inlineStyle->isMutable());
        static_pointer_cast<MutableStylePropertySet>(inlineStyle)->parseDeclaration(newStyleString, document().elementSheet().contents());
    }
}

void Element::styleAttributeChanged(const AtomicString& newStyleString, AttributeModificationReason modificationReason)
{
    ASSERT(isStyledElement());
    WTF::OrdinalNumber startLineNumber = WTF::OrdinalNumber::beforeFirst();
    if (document().scriptableDocumentParser() && !document().isInDocumentWrite())
        startLineNumber = document().scriptableDocumentParser()->lineNumber();

    if (newStyleString.isNull()) {
        ensureUniqueElementData().m_inlineStyle.clear();
    } else if (modificationReason == ModifiedByCloning || document().contentSecurityPolicy()->allowInlineStyle(document().url(), startLineNumber)) {
        setInlineStyleFromString(newStyleString);
    }

    elementData()->m_styleAttributeIsDirty = false;

    setNeedsStyleRecalc(LocalStyleChange);
    InspectorInstrumentation::didInvalidateStyleAttr(this);
}

void Element::inlineStyleChanged()
{
    ASSERT(isStyledElement());
    setNeedsStyleRecalc(LocalStyleChange);
    ASSERT(elementData());
    elementData()->m_styleAttributeIsDirty = true;
    InspectorInstrumentation::didInvalidateStyleAttr(this);
}

bool Element::setInlineStyleProperty(CSSPropertyID propertyID, CSSValueID identifier, bool important)
{
    ASSERT(isStyledElement());
    ensureMutableInlineStyle().setProperty(propertyID, cssValuePool().createIdentifierValue(identifier), important);
    inlineStyleChanged();
    return true;
}

bool Element::setInlineStyleProperty(CSSPropertyID propertyID, CSSPropertyID identifier, bool important)
{
    ASSERT(isStyledElement());
    ensureMutableInlineStyle().setProperty(propertyID, cssValuePool().createIdentifierValue(identifier), important);
    inlineStyleChanged();
    return true;
}

bool Element::setInlineStyleProperty(CSSPropertyID propertyID, double value, CSSPrimitiveValue::UnitTypes unit, bool important)
{
    ASSERT(isStyledElement());
    ensureMutableInlineStyle().setProperty(propertyID, cssValuePool().createValue(value, unit), important);
    inlineStyleChanged();
    return true;
}

bool Element::setInlineStyleProperty(CSSPropertyID propertyID, const String& value, bool important)
{
    ASSERT(isStyledElement());
    bool changes = ensureMutableInlineStyle().setProperty(propertyID, value, important, document().elementSheet().contents());
    if (changes)
        inlineStyleChanged();
    return changes;
}

bool Element::removeInlineStyleProperty(CSSPropertyID propertyID)
{
    ASSERT(isStyledElement());
    if (!inlineStyle())
        return false;
    bool changes = ensureMutableInlineStyle().removeProperty(propertyID);
    if (changes)
        inlineStyleChanged();
    return changes;
}

void Element::removeAllInlineStyleProperties()
{
    ASSERT(isStyledElement());
    if (!inlineStyle())
        return;
    ensureMutableInlineStyle().clear();
    inlineStyleChanged();
}

void Element::updatePresentationAttributeStyle()
{
    // ShareableElementData doesn't store presentation attribute style, so make sure we have a UniqueElementData.
    UniqueElementData& elementData = ensureUniqueElementData();
    elementData.m_presentationAttributeStyleIsDirty = false;
    elementData.m_presentationAttributeStyle = computePresentationAttributeStyle(*this);
}

void Element::addPropertyToPresentationAttributeStyle(MutableStylePropertySet* style, CSSPropertyID propertyID, CSSValueID identifier)
{
    ASSERT(isStyledElement());
    style->setProperty(propertyID, cssValuePool().createIdentifierValue(identifier));
}

void Element::addPropertyToPresentationAttributeStyle(MutableStylePropertySet* style, CSSPropertyID propertyID, double value, CSSPrimitiveValue::UnitTypes unit)
{
    ASSERT(isStyledElement());
    style->setProperty(propertyID, cssValuePool().createValue(value, unit));
}

void Element::addPropertyToPresentationAttributeStyle(MutableStylePropertySet* style, CSSPropertyID propertyID, const String& value)
{
    ASSERT(isStyledElement());
    style->setProperty(propertyID, value, false);
}

bool Element::supportsStyleSharing() const
{
    if (!isStyledElement() || !parentOrShadowHostElement())
        return false;
    // If the element has inline style it is probably unique.
    if (inlineStyle())
        return false;
    if (isSVGElement() && toSVGElement(this)->animatedSMILStyleProperties())
        return false;
    // Ids stop style sharing if they show up in the stylesheets.
    if (hasID() && document().ensureStyleResolver().hasRulesForId(idForStyleResolution()))
        return false;
    // Active and hovered elements always make a chain towards the document node
    // and no siblings or cousins will have the same state.
    if (hovered())
        return false;
    if (active())
        return false;
    if (focused())
        return false;
    if (!parentOrShadowHostElement()->childrenSupportStyleSharing())
        return false;
    if (hasScopedHTMLStyleChild())
        return false;
    if (this == document().cssTarget())
        return false;
    if (isHTMLElement() && toHTMLElement(this)->hasDirectionAuto())
        return false;
    if (hasActiveAnimations())
        return false;
    // Turn off style sharing for elements that can gain layers for reasons outside of the style system.
    // See comments in RenderObject::setStyle().
    // FIXME: Why does gaining a layer from outside the style system require disabling sharing?
    if (isHTMLFrameElementBase(*this)
        || isHTMLEmbedElement(*this)
        || isHTMLObjectElement(*this)
        || isHTMLAppletElement(*this)
        || isHTMLCanvasElement(*this))
        return false;
    if (FullscreenElementStack::isActiveFullScreenElement(this))
        return false;
    return true;
}

} // namespace WebCore