cc/layers/layer

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This source file includes following definitions.
current_draw_mode_
AddChild
RemoveChild
SetParent
ClearChildList
HasAncestor
SetScrollParent
SetDebugInfo
SetScrollChildren
SetClipParent
SetClipChildren
PassCopyRequests
TakeCopyRequestsAndTransformToTarget
CreateRenderSurface
ClearRenderSurface
CreateSharedQuadState
WillDraw
DidDraw
ShowDebugBorders
GetDebugBorderProperties
AppendDebugBorderQuad
AppendDebugBorderQuad
HasDelegatedContent
HasContributingDelegatedRenderPasses
FirstContributingRenderPassId
NextContributingRenderPassId
ContentsResourceId
SetSentScrollDelta
ScrollBy
SetScrollClipLayer
ApplySentScrollDeltasFromAbortedCommit
ApplyScrollDeltasSinceBeginMainFrame
TryScroll
LayerRectToContentRect
GetPicture
AreVisibleResourcesReady
CreateLayerImpl
PushPropertiesTo
FixedContainerSizeDelta
LayerTreeAsJson
SetStackingOrderChanged
NoteLayerPropertyChanged
NoteLayerPropertyChangedForSubtree
NoteLayerPropertyChangedForDescendantsInternal
NoteLayerPropertyChangedForDescendants
LayerTypeAsString
ResetAllChangeTrackingForSubtree
ScrollOffsetForAnimation
OnFilterAnimated
OnOpacityAnimated
OnTransformAnimated
OnScrollOffsetAnimated
OnAnimationWaitingForDeletion
IsActive
bounds
SetBounds
SetTemporaryImplBounds
SetMaskLayer
TakeMaskLayer
SetReplicaLayer
TakeReplicaLayer
ToScrollbarLayer
SetDrawsContent
SetHideLayerAndSubtree
SetAnchorPoint
SetAnchorPointZ
SetBackgroundColor
SafeOpaqueBackgroundColor
SetFilters
FilterIsAnimating
FilterIsAnimatingOnImplOnly
SetBackgroundFilters
SetMasksToBounds
SetContentsOpaque
SetOpacity
OpacityIsAnimating
OpacityIsAnimatingOnImplOnly
SetBlendMode
SetIsRootForIsolatedGroup
SetPosition
SetShouldFlattenTransform
SetIs3dSorted
SetTransform
TransformIsAnimating
TransformIsAnimatingOnImplOnly
SetUpdateRect
SetContentBounds
SetContentsScale
CalculateContentsScale
SetScrollOffsetDelegate
IsExternalFlingActive
SetScrollOffset
SetScrollOffsetAndDelta
ScrollDelta
SetScrollDelta
TotalScrollOffset
SetDoubleSided
VisibleContentOpaqueRegion
DidBeginTracing
ReleaseResources
MaxScrollOffset
ClampScrollToMaxScrollOffset
SetScrollbarPosition
DidBecomeActive
ClearScrollbars
AddScrollbar
RemoveScrollbar
HasScrollbar
ScrollbarParametersDidChange
SetNeedsPushProperties
AddDependentNeedsPushProperties
RemoveDependentNeedsPushProperties
AsValueInto
GPUMemoryUsageInBytes
AsValue
RunMicroBenchmark
// Copyright 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "cc/layers/layer_impl.h"

#include "base/debug/trace_event.h"
#include "base/json/json_reader.h"
#include "base/strings/stringprintf.h"
#include "cc/animation/animation_registrar.h"
#include "cc/animation/scrollbar_animation_controller.h"
#include "cc/animation/scrollbar_animation_controller_linear_fade.h"
#include "cc/animation/scrollbar_animation_controller_thinning.h"
#include "cc/base/math_util.h"
#include "cc/debug/debug_colors.h"
#include "cc/debug/layer_tree_debug_state.h"
#include "cc/debug/micro_benchmark_impl.h"
#include "cc/debug/traced_value.h"
#include "cc/input/layer_scroll_offset_delegate.h"
#include "cc/layers/layer_utils.h"
#include "cc/layers/painted_scrollbar_layer_impl.h"
#include "cc/layers/quad_sink.h"
#include "cc/output/copy_output_request.h"
#include "cc/quads/debug_border_draw_quad.h"
#include "cc/trees/layer_tree_host_common.h"
#include "cc/trees/layer_tree_impl.h"
#include "cc/trees/layer_tree_settings.h"
#include "cc/trees/proxy.h"
#include "ui/gfx/box_f.h"
#include "ui/gfx/geometry/vector2d_conversions.h"
#include "ui/gfx/point_conversions.h"
#include "ui/gfx/quad_f.h"
#include "ui/gfx/rect_conversions.h"
#include "ui/gfx/size_conversions.h"

namespace cc {
LayerImpl::LayerImpl(LayerTreeImpl* tree_impl, int id)
    : parent_(NULL),
      scroll_parent_(NULL),
      clip_parent_(NULL),
      mask_layer_id_(-1),
      replica_layer_id_(-1),
      layer_id_(id),
      layer_tree_impl_(tree_impl),
      anchor_point_(0.5f, 0.5f),
      anchor_point_z_(0.f),
      scroll_offset_delegate_(NULL),
      scroll_clip_layer_(NULL),
      should_scroll_on_main_thread_(false),
      have_wheel_event_handlers_(false),
      have_scroll_event_handlers_(false),
      user_scrollable_horizontal_(true),
      user_scrollable_vertical_(true),
      stacking_order_changed_(false),
      double_sided_(true),
      should_flatten_transform_(true),
      layer_property_changed_(false),
      masks_to_bounds_(false),
      contents_opaque_(false),
      is_root_for_isolated_group_(false),
      use_parent_backface_visibility_(false),
      draw_checkerboard_for_missing_tiles_(false),
      draws_content_(false),
      hide_layer_and_subtree_(false),
      force_render_surface_(false),
      is_container_for_fixed_position_layers_(false),
      is_3d_sorted_(false),
      background_color_(0),
      opacity_(1.0),
      blend_mode_(SkXfermode::kSrcOver_Mode),
      draw_depth_(0.f),
      needs_push_properties_(false),
      num_dependents_need_push_properties_(0),
      current_draw_mode_(DRAW_MODE_NONE) {
  DCHECK_GT(layer_id_, 0);
  DCHECK(layer_tree_impl_);
  layer_tree_impl_->RegisterLayer(this);
  AnimationRegistrar* registrar = layer_tree_impl_->animationRegistrar();
  layer_animation_controller_ =
      registrar->GetAnimationControllerForId(layer_id_);
  layer_animation_controller_->AddValueObserver(this);
  if (IsActive())
    layer_animation_controller_->set_value_provider(this);
  SetNeedsPushProperties();
}

LayerImpl::~LayerImpl() {
  DCHECK_EQ(DRAW_MODE_NONE, current_draw_mode_);

  layer_animation_controller_->RemoveValueObserver(this);
  layer_animation_controller_->remove_value_provider(this);

  if (!copy_requests_.empty() && layer_tree_impl_->IsActiveTree())
    layer_tree_impl()->RemoveLayerWithCopyOutputRequest(this);
  layer_tree_impl_->UnregisterLayer(this);

  TRACE_EVENT_OBJECT_DELETED_WITH_ID(
      TRACE_DISABLED_BY_DEFAULT("cc.debug"), "cc::LayerImpl", this);
}

void LayerImpl::AddChild(scoped_ptr<LayerImpl> child) {
  child->SetParent(this);
  DCHECK_EQ(layer_tree_impl(), child->layer_tree_impl());
  children_.push_back(child.Pass());
  layer_tree_impl()->set_needs_update_draw_properties();
}

scoped_ptr<LayerImpl> LayerImpl::RemoveChild(LayerImpl* child) {
  for (OwnedLayerImplList::iterator it = children_.begin();
       it != children_.end();
       ++it) {
    if (*it == child) {
      scoped_ptr<LayerImpl> ret = children_.take(it);
      children_.erase(it);
      layer_tree_impl()->set_needs_update_draw_properties();
      return ret.Pass();
    }
  }
  return scoped_ptr<LayerImpl>();
}

void LayerImpl::SetParent(LayerImpl* parent) {
  if (parent_should_know_need_push_properties()) {
    if (parent_)
      parent_->RemoveDependentNeedsPushProperties();
    if (parent)
      parent->AddDependentNeedsPushProperties();
  }
  parent_ = parent;
}

void LayerImpl::ClearChildList() {
  if (children_.empty())
    return;

  children_.clear();
  layer_tree_impl()->set_needs_update_draw_properties();
}

bool LayerImpl::HasAncestor(const LayerImpl* ancestor) const {
  if (!ancestor)
    return false;

  for (const LayerImpl* layer = this; layer; layer = layer->parent()) {
    if (layer == ancestor)
      return true;
  }

  return false;
}

void LayerImpl::SetScrollParent(LayerImpl* parent) {
  if (scroll_parent_ == parent)
    return;

  // Having both a scroll parent and a scroll offset delegate is unsupported.
  DCHECK(!scroll_offset_delegate_);

  if (parent)
    DCHECK_EQ(layer_tree_impl()->LayerById(parent->id()), parent);

  scroll_parent_ = parent;
  SetNeedsPushProperties();
}

void LayerImpl::SetDebugInfo(
    scoped_refptr<base::debug::ConvertableToTraceFormat> other) {
  debug_info_ = other;
  SetNeedsPushProperties();
}

void LayerImpl::SetScrollChildren(std::set<LayerImpl*>* children) {
  if (scroll_children_.get() == children)
    return;
  scroll_children_.reset(children);
  SetNeedsPushProperties();
}

void LayerImpl::SetClipParent(LayerImpl* ancestor) {
  if (clip_parent_ == ancestor)
    return;

  clip_parent_ = ancestor;
  SetNeedsPushProperties();
}

void LayerImpl::SetClipChildren(std::set<LayerImpl*>* children) {
  if (clip_children_.get() == children)
    return;
  clip_children_.reset(children);
  SetNeedsPushProperties();
}

void LayerImpl::PassCopyRequests(ScopedPtrVector<CopyOutputRequest>* requests) {
  if (requests->empty())
    return;

  bool was_empty = copy_requests_.empty();
  copy_requests_.insert_and_take(copy_requests_.end(), *requests);
  requests->clear();

  if (was_empty && layer_tree_impl()->IsActiveTree())
    layer_tree_impl()->AddLayerWithCopyOutputRequest(this);
  NoteLayerPropertyChangedForSubtree();
}

void LayerImpl::TakeCopyRequestsAndTransformToTarget(
    ScopedPtrVector<CopyOutputRequest>* requests) {
  DCHECK(!copy_requests_.empty());
  DCHECK(layer_tree_impl()->IsActiveTree());

  size_t first_inserted_request = requests->size();
  requests->insert_and_take(requests->end(), copy_requests_);
  copy_requests_.clear();

  for (size_t i = first_inserted_request; i < requests->size(); ++i) {
    CopyOutputRequest* request = requests->at(i);
    if (!request->has_area())
      continue;

    gfx::Rect request_in_layer_space = request->area();
    gfx::Rect request_in_content_space =
        LayerRectToContentRect(request_in_layer_space);
    request->set_area(MathUtil::MapEnclosingClippedRect(
        draw_properties_.target_space_transform, request_in_content_space));
  }

  layer_tree_impl()->RemoveLayerWithCopyOutputRequest(this);
}

void LayerImpl::CreateRenderSurface() {
  DCHECK(!draw_properties_.render_surface);
  draw_properties_.render_surface =
      make_scoped_ptr(new RenderSurfaceImpl(this));
  draw_properties_.render_target = this;
}

void LayerImpl::ClearRenderSurface() {
  draw_properties_.render_surface.reset();
}

scoped_ptr<SharedQuadState> LayerImpl::CreateSharedQuadState() const {
  scoped_ptr<SharedQuadState> state = SharedQuadState::Create();
  state->SetAll(draw_properties_.target_space_transform,
                draw_properties_.content_bounds,
                draw_properties_.visible_content_rect,
                draw_properties_.clip_rect,
                draw_properties_.is_clipped,
                draw_properties_.opacity,
                blend_mode_);
  return state.Pass();
}

bool LayerImpl::WillDraw(DrawMode draw_mode,
                         ResourceProvider* resource_provider) {
  // WillDraw/DidDraw must be matched.
  DCHECK_NE(DRAW_MODE_NONE, draw_mode);
  DCHECK_EQ(DRAW_MODE_NONE, current_draw_mode_);
  current_draw_mode_ = draw_mode;
  return true;
}

void LayerImpl::DidDraw(ResourceProvider* resource_provider) {
  DCHECK_NE(DRAW_MODE_NONE, current_draw_mode_);
  current_draw_mode_ = DRAW_MODE_NONE;
}

bool LayerImpl::ShowDebugBorders() const {
  return layer_tree_impl()->debug_state().show_debug_borders;
}

void LayerImpl::GetDebugBorderProperties(SkColor* color, float* width) const {
  if (draws_content_) {
    *color = DebugColors::ContentLayerBorderColor();
    *width = DebugColors::ContentLayerBorderWidth(layer_tree_impl());
    return;
  }

  if (masks_to_bounds_) {
    *color = DebugColors::MaskingLayerBorderColor();
    *width = DebugColors::MaskingLayerBorderWidth(layer_tree_impl());
    return;
  }

  *color = DebugColors::ContainerLayerBorderColor();
  *width = DebugColors::ContainerLayerBorderWidth(layer_tree_impl());
}

void LayerImpl::AppendDebugBorderQuad(
    QuadSink* quad_sink,
    const SharedQuadState* shared_quad_state,
    AppendQuadsData* append_quads_data) const {
  SkColor color;
  float width;
  GetDebugBorderProperties(&color, &width);
  AppendDebugBorderQuad(
      quad_sink, shared_quad_state, append_quads_data, color, width);
}

void LayerImpl::AppendDebugBorderQuad(QuadSink* quad_sink,
                                      const SharedQuadState* shared_quad_state,
                                      AppendQuadsData* append_quads_data,
                                      SkColor color,
                                      float width) const {
  if (!ShowDebugBorders())
    return;

  gfx::Rect quad_rect(content_bounds());
  gfx::Rect visible_quad_rect(quad_rect);
  scoped_ptr<DebugBorderDrawQuad> debug_border_quad =
      DebugBorderDrawQuad::Create();
  debug_border_quad->SetNew(
      shared_quad_state, quad_rect, visible_quad_rect, color, width);
  quad_sink->Append(debug_border_quad.PassAs<DrawQuad>());
}

bool LayerImpl::HasDelegatedContent() const {
  return false;
}

bool LayerImpl::HasContributingDelegatedRenderPasses() const {
  return false;
}

RenderPass::Id LayerImpl::FirstContributingRenderPassId() const {
  return RenderPass::Id(0, 0);
}

RenderPass::Id LayerImpl::NextContributingRenderPassId(RenderPass::Id id)
    const {
  return RenderPass::Id(0, 0);
}

ResourceProvider::ResourceId LayerImpl::ContentsResourceId() const {
  NOTREACHED();
  return 0;
}

void LayerImpl::SetSentScrollDelta(const gfx::Vector2d& sent_scroll_delta) {
  // Pending tree never has sent scroll deltas
  DCHECK(layer_tree_impl()->IsActiveTree());

  if (sent_scroll_delta_ == sent_scroll_delta)
    return;

  sent_scroll_delta_ = sent_scroll_delta;
}

gfx::Vector2dF LayerImpl::ScrollBy(const gfx::Vector2dF& scroll) {
  DCHECK(scrollable());
  gfx::Vector2dF min_delta = -scroll_offset_;
  gfx::Vector2dF max_delta = MaxScrollOffset() - scroll_offset_;
  // Clamp new_delta so that position + delta stays within scroll bounds.
  gfx::Vector2dF new_delta = (ScrollDelta() + scroll);
  new_delta.SetToMax(min_delta);
  new_delta.SetToMin(max_delta);
  gfx::Vector2dF unscrolled =
      ScrollDelta() + scroll - new_delta;
  SetScrollDelta(new_delta);

  return unscrolled;
}

void LayerImpl::SetScrollClipLayer(int scroll_clip_layer_id) {
  scroll_clip_layer_ = layer_tree_impl()->LayerById(scroll_clip_layer_id);
}

void LayerImpl::ApplySentScrollDeltasFromAbortedCommit() {
  // Pending tree never has sent scroll deltas
  DCHECK(layer_tree_impl()->IsActiveTree());

  // Apply sent scroll deltas to scroll position / scroll delta as if the
  // main thread had applied them and then committed those values.
  //
  // This function should not change the total scroll offset; it just shifts
  // some of the scroll delta to the scroll offset.  Therefore, adjust these
  // variables directly rather than calling the scroll offset delegate to
  // avoid sending it multiple spurious calls.
  //
  // Because of the way scroll delta is calculated with a delegate, this will
  // leave the total scroll offset unchanged on this layer regardless of
  // whether a delegate is being used.
  scroll_offset_ += sent_scroll_delta_;
  scroll_delta_ -= sent_scroll_delta_;
  sent_scroll_delta_ = gfx::Vector2d();
}

void LayerImpl::ApplyScrollDeltasSinceBeginMainFrame() {
  // Only the pending tree can have missing scrolls.
  DCHECK(layer_tree_impl()->IsPendingTree());
  if (!scrollable())
    return;

  // Pending tree should never have sent scroll deltas.
  DCHECK(sent_scroll_delta().IsZero());

  LayerImpl* active_twin = layer_tree_impl()->FindActiveTreeLayerById(id());
  if (active_twin) {
    // Scrolls that happens after begin frame (where the sent scroll delta
    // comes from) and commit need to be applied to the pending tree
    // so that it is up to date with the total scroll.
    SetScrollDelta(active_twin->ScrollDelta() -
                   active_twin->sent_scroll_delta());
  }
}

InputHandler::ScrollStatus LayerImpl::TryScroll(
    const gfx::PointF& screen_space_point,
    InputHandler::ScrollInputType type) const {
  if (should_scroll_on_main_thread()) {
    TRACE_EVENT0("cc", "LayerImpl::TryScroll: Failed ShouldScrollOnMainThread");
    return InputHandler::ScrollOnMainThread;
  }

  if (!screen_space_transform().IsInvertible()) {
    TRACE_EVENT0("cc", "LayerImpl::TryScroll: Ignored NonInvertibleTransform");
    return InputHandler::ScrollIgnored;
  }

  if (!non_fast_scrollable_region().IsEmpty()) {
    bool clipped = false;
    gfx::Transform inverse_screen_space_transform(
        gfx::Transform::kSkipInitialization);
    if (!screen_space_transform().GetInverse(&inverse_screen_space_transform)) {
      // TODO(shawnsingh): We shouldn't be applying a projection if screen space
      // transform is uninvertible here. Perhaps we should be returning
      // ScrollOnMainThread in this case?
    }

    gfx::PointF hit_test_point_in_content_space =
        MathUtil::ProjectPoint(inverse_screen_space_transform,
                               screen_space_point,
                               &clipped);
    gfx::PointF hit_test_point_in_layer_space =
        gfx::ScalePoint(hit_test_point_in_content_space,
                        1.f / contents_scale_x(),
                        1.f / contents_scale_y());
    if (!clipped &&
        non_fast_scrollable_region().Contains(
            gfx::ToRoundedPoint(hit_test_point_in_layer_space))) {
      TRACE_EVENT0("cc",
                   "LayerImpl::tryScroll: Failed NonFastScrollableRegion");
      return InputHandler::ScrollOnMainThread;
    }
  }

  if (type == InputHandler::Wheel && have_wheel_event_handlers()) {
    TRACE_EVENT0("cc", "LayerImpl::tryScroll: Failed WheelEventHandlers");
    return InputHandler::ScrollOnMainThread;
  }

  if (!scrollable()) {
    TRACE_EVENT0("cc", "LayerImpl::tryScroll: Ignored not scrollable");
    return InputHandler::ScrollIgnored;
  }

  gfx::Vector2d max_scroll_offset = MaxScrollOffset();
  if (max_scroll_offset.x() <= 0 && max_scroll_offset.y() <= 0) {
    TRACE_EVENT0("cc",
                 "LayerImpl::tryScroll: Ignored. Technically scrollable,"
                 " but has no affordance in either direction.");
    return InputHandler::ScrollIgnored;
  }

  return InputHandler::ScrollStarted;
}

gfx::Rect LayerImpl::LayerRectToContentRect(
    const gfx::RectF& layer_rect) const {
  gfx::RectF content_rect =
      gfx::ScaleRect(layer_rect, contents_scale_x(), contents_scale_y());
  // Intersect with content rect to avoid the extra pixel because for some
  // values x and y, ceil((x / y) * y) may be x + 1.
  content_rect.Intersect(gfx::Rect(content_bounds()));
  return gfx::ToEnclosingRect(content_rect);
}

skia::RefPtr<SkPicture> LayerImpl::GetPicture() {
  return skia::RefPtr<SkPicture>();
}

bool LayerImpl::AreVisibleResourcesReady() const {
  return true;
}

scoped_ptr<LayerImpl> LayerImpl::CreateLayerImpl(LayerTreeImpl* tree_impl) {
  return LayerImpl::Create(tree_impl, layer_id_);
}

void LayerImpl::PushPropertiesTo(LayerImpl* layer) {
  layer->SetAnchorPoint(anchor_point_);
  layer->SetAnchorPointZ(anchor_point_z_);
  layer->SetBackgroundColor(background_color_);
  layer->SetBounds(bounds_);
  layer->SetContentBounds(content_bounds());
  layer->SetContentsScale(contents_scale_x(), contents_scale_y());
  layer->SetDoubleSided(double_sided_);
  layer->SetDrawCheckerboardForMissingTiles(
      draw_checkerboard_for_missing_tiles_);
  layer->SetForceRenderSurface(force_render_surface_);
  layer->SetDrawsContent(DrawsContent());
  layer->SetHideLayerAndSubtree(hide_layer_and_subtree_);
  layer->SetFilters(filters());
  layer->SetBackgroundFilters(background_filters());
  layer->SetMasksToBounds(masks_to_bounds_);
  layer->SetShouldScrollOnMainThread(should_scroll_on_main_thread_);
  layer->SetHaveWheelEventHandlers(have_wheel_event_handlers_);
  layer->SetHaveScrollEventHandlers(have_scroll_event_handlers_);
  layer->SetNonFastScrollableRegion(non_fast_scrollable_region_);
  layer->SetTouchEventHandlerRegion(touch_event_handler_region_);
  layer->SetContentsOpaque(contents_opaque_);
  layer->SetOpacity(opacity_);
  layer->SetBlendMode(blend_mode_);
  layer->SetIsRootForIsolatedGroup(is_root_for_isolated_group_);
  layer->SetPosition(position_);
  layer->SetIsContainerForFixedPositionLayers(
      is_container_for_fixed_position_layers_);
  layer->SetPositionConstraint(position_constraint_);
  layer->SetShouldFlattenTransform(should_flatten_transform_);
  layer->SetIs3dSorted(is_3d_sorted_);
  layer->SetUseParentBackfaceVisibility(use_parent_backface_visibility_);
  layer->SetTransform(transform_);

  layer->SetScrollClipLayer(scroll_clip_layer_ ? scroll_clip_layer_->id()
                                               : Layer::INVALID_ID);
  layer->set_user_scrollable_horizontal(user_scrollable_horizontal_);
  layer->set_user_scrollable_vertical(user_scrollable_vertical_);
  layer->SetScrollOffsetAndDelta(
      scroll_offset_, layer->ScrollDelta() - layer->sent_scroll_delta());
  layer->SetSentScrollDelta(gfx::Vector2d());

  LayerImpl* scroll_parent = NULL;
  if (scroll_parent_) {
    scroll_parent = layer->layer_tree_impl()->LayerById(scroll_parent_->id());
    DCHECK(scroll_parent);
  }

  layer->SetScrollParent(scroll_parent);
  if (scroll_children_) {
    std::set<LayerImpl*>* scroll_children = new std::set<LayerImpl*>;
    for (std::set<LayerImpl*>::iterator it = scroll_children_->begin();
         it != scroll_children_->end();
         ++it) {
      DCHECK_EQ((*it)->scroll_parent(), this);
      LayerImpl* scroll_child =
          layer->layer_tree_impl()->LayerById((*it)->id());
      DCHECK(scroll_child);
      scroll_children->insert(scroll_child);
    }
    layer->SetScrollChildren(scroll_children);
  } else {
    layer->SetScrollChildren(NULL);
  }

  LayerImpl* clip_parent = NULL;
  if (clip_parent_) {
    clip_parent = layer->layer_tree_impl()->LayerById(
        clip_parent_->id());
    DCHECK(clip_parent);
  }

  layer->SetClipParent(clip_parent);
  if (clip_children_) {
    std::set<LayerImpl*>* clip_children = new std::set<LayerImpl*>;
    for (std::set<LayerImpl*>::iterator it = clip_children_->begin();
        it != clip_children_->end(); ++it)
      clip_children->insert(layer->layer_tree_impl()->LayerById((*it)->id()));
    layer->SetClipChildren(clip_children);
  } else {
    layer->SetClipChildren(NULL);
  }

  layer->PassCopyRequests(&copy_requests_);

  // If the main thread commits multiple times before the impl thread actually
  // draws, then damage tracking will become incorrect if we simply clobber the
  // update_rect here. The LayerImpl's update_rect needs to accumulate (i.e.
  // union) any update changes that have occurred on the main thread.
  update_rect_.Union(layer->update_rect());
  layer->SetUpdateRect(update_rect_);

  layer->SetStackingOrderChanged(stacking_order_changed_);
  layer->SetDebugInfo(debug_info_);

  // Reset any state that should be cleared for the next update.
  stacking_order_changed_ = false;
  update_rect_ = gfx::RectF();
  needs_push_properties_ = false;
  num_dependents_need_push_properties_ = 0;
}

gfx::Vector2dF LayerImpl::FixedContainerSizeDelta() const {
  if (!scroll_clip_layer_)
    return gfx::Vector2dF();

  float scale_delta = layer_tree_impl()->page_scale_delta();
  float scale = layer_tree_impl()->page_scale_factor();

  gfx::Vector2dF delta_from_scroll = scroll_clip_layer_->BoundsDelta();
  delta_from_scroll.Scale(1.f / scale);

  // The delta-from-pinch component requires some explanation: A viewport of
  // size (w,h) will appear to be size (w/s,h/s) under scale s in the content
  // space. If s -> s' on the impl thread, where s' = s * ds, then the apparent
  // viewport size change in the content space due to ds is:
  //
  // (w/s',h/s') - (w/s,h/s) = (w,h)(1/s' - 1/s) = (w,h)(1 - ds)/(s ds)
  //
  gfx::Vector2dF delta_from_pinch =
      gfx::Rect(scroll_clip_layer_->bounds()).bottom_right() - gfx::PointF();
  delta_from_pinch.Scale((1.f - scale_delta) / (scale * scale_delta));

  return delta_from_scroll + delta_from_pinch;
}

base::DictionaryValue* LayerImpl::LayerTreeAsJson() const {
  base::DictionaryValue* result = new base::DictionaryValue;
  result->SetString("LayerType", LayerTypeAsString());

  base::ListValue* list = new base::ListValue;
  list->AppendInteger(bounds().width());
  list->AppendInteger(bounds().height());
  result->Set("Bounds", list);

  list = new base::ListValue;
  list->AppendDouble(position_.x());
  list->AppendDouble(position_.y());
  result->Set("Position", list);

  const gfx::Transform& gfx_transform = draw_properties_.target_space_transform;
  double transform[16];
  gfx_transform.matrix().asColMajord(transform);
  list = new base::ListValue;
  for (int i = 0; i < 16; ++i)
    list->AppendDouble(transform[i]);
  result->Set("DrawTransform", list);

  result->SetBoolean("DrawsContent", draws_content_);
  result->SetDouble("Opacity", opacity());
  result->SetBoolean("ContentsOpaque", contents_opaque_);

  if (scrollable())
    result->SetBoolean("Scrollable", true);

  if (have_wheel_event_handlers_)
    result->SetBoolean("WheelHandler", have_wheel_event_handlers_);
  if (have_scroll_event_handlers_)
    result->SetBoolean("ScrollHandler", have_scroll_event_handlers_);
  if (!touch_event_handler_region_.IsEmpty()) {
    scoped_ptr<base::Value> region = touch_event_handler_region_.AsValue();
    result->Set("TouchRegion", region.release());
  }

  list = new base::ListValue;
  for (size_t i = 0; i < children_.size(); ++i)
    list->Append(children_[i]->LayerTreeAsJson());
  result->Set("Children", list);

  return result;
}

void LayerImpl::SetStackingOrderChanged(bool stacking_order_changed) {
  if (stacking_order_changed) {
    stacking_order_changed_ = true;
    NoteLayerPropertyChangedForSubtree();
  }
}

void LayerImpl::NoteLayerPropertyChanged() {
  layer_property_changed_ = true;
  layer_tree_impl()->set_needs_update_draw_properties();
  SetNeedsPushProperties();
}

void LayerImpl::NoteLayerPropertyChangedForSubtree() {
  layer_property_changed_ = true;
  layer_tree_impl()->set_needs_update_draw_properties();
  for (size_t i = 0; i < children_.size(); ++i)
    children_[i]->NoteLayerPropertyChangedForDescendantsInternal();
  SetNeedsPushProperties();
}

void LayerImpl::NoteLayerPropertyChangedForDescendantsInternal() {
  layer_property_changed_ = true;
  for (size_t i = 0; i < children_.size(); ++i)
    children_[i]->NoteLayerPropertyChangedForDescendantsInternal();
}

void LayerImpl::NoteLayerPropertyChangedForDescendants() {
  layer_tree_impl()->set_needs_update_draw_properties();
  for (size_t i = 0; i < children_.size(); ++i)
    children_[i]->NoteLayerPropertyChangedForDescendantsInternal();
  SetNeedsPushProperties();
}

const char* LayerImpl::LayerTypeAsString() const {
  return "cc::LayerImpl";
}

void LayerImpl::ResetAllChangeTrackingForSubtree() {
  layer_property_changed_ = false;

  update_rect_ = gfx::RectF();

  if (draw_properties_.render_surface)
    draw_properties_.render_surface->ResetPropertyChangedFlag();

  if (mask_layer_)
    mask_layer_->ResetAllChangeTrackingForSubtree();

  if (replica_layer_) {
    // This also resets the replica mask, if it exists.
    replica_layer_->ResetAllChangeTrackingForSubtree();
  }

  for (size_t i = 0; i < children_.size(); ++i)
    children_[i]->ResetAllChangeTrackingForSubtree();

  needs_push_properties_ = false;
  num_dependents_need_push_properties_ = 0;
}

gfx::Vector2dF LayerImpl::ScrollOffsetForAnimation() const {
  return TotalScrollOffset();
}

void LayerImpl::OnFilterAnimated(const FilterOperations& filters) {
  SetFilters(filters);
}

void LayerImpl::OnOpacityAnimated(float opacity) {
  SetOpacity(opacity);
}

void LayerImpl::OnTransformAnimated(const gfx::Transform& transform) {
  SetTransform(transform);
}

void LayerImpl::OnScrollOffsetAnimated(const gfx::Vector2dF& scroll_offset) {
  // Only layers in the active tree should need to do anything here, since
  // layers in the pending tree will find out about these changes as a
  // result of the call to SetScrollDelta.
  if (!IsActive())
    return;

  SetScrollDelta(scroll_offset - scroll_offset_);

  layer_tree_impl_->DidAnimateScrollOffset();
}

void LayerImpl::OnAnimationWaitingForDeletion() {}

bool LayerImpl::IsActive() const {
  return layer_tree_impl_->IsActiveTree();
}

// TODO(wjmaclean) Convert so that bounds returns SizeF.
gfx::Size LayerImpl::bounds() const {
  return ToFlooredSize(temporary_impl_bounds_);
}

void LayerImpl::SetBounds(const gfx::Size& bounds) {
  if (bounds_ == bounds)
    return;

  bounds_ = bounds;
  temporary_impl_bounds_ = bounds;

  ScrollbarParametersDidChange();
  if (masks_to_bounds())
    NoteLayerPropertyChangedForSubtree();
  else
    NoteLayerPropertyChanged();
}

void LayerImpl::SetTemporaryImplBounds(const gfx::SizeF& bounds) {
  if (temporary_impl_bounds_ == bounds)
    return;

  temporary_impl_bounds_ = bounds;

  ScrollbarParametersDidChange();
  if (masks_to_bounds())
    NoteLayerPropertyChangedForSubtree();
  else
    NoteLayerPropertyChanged();
}

void LayerImpl::SetMaskLayer(scoped_ptr<LayerImpl> mask_layer) {
  int new_layer_id = mask_layer ? mask_layer->id() : -1;

  if (mask_layer) {
    DCHECK_EQ(layer_tree_impl(), mask_layer->layer_tree_impl());
    DCHECK_NE(new_layer_id, mask_layer_id_);
  } else if (new_layer_id == mask_layer_id_) {
    return;
  }

  mask_layer_ = mask_layer.Pass();
  mask_layer_id_ = new_layer_id;
  if (mask_layer_)
    mask_layer_->SetParent(this);
  NoteLayerPropertyChangedForSubtree();
}

scoped_ptr<LayerImpl> LayerImpl::TakeMaskLayer() {
  mask_layer_id_ = -1;
  return mask_layer_.Pass();
}

void LayerImpl::SetReplicaLayer(scoped_ptr<LayerImpl> replica_layer) {
  int new_layer_id = replica_layer ? replica_layer->id() : -1;

  if (replica_layer) {
    DCHECK_EQ(layer_tree_impl(), replica_layer->layer_tree_impl());
    DCHECK_NE(new_layer_id, replica_layer_id_);
  } else if (new_layer_id == replica_layer_id_) {
    return;
  }

  replica_layer_ = replica_layer.Pass();
  replica_layer_id_ = new_layer_id;
  if (replica_layer_)
    replica_layer_->SetParent(this);
  NoteLayerPropertyChangedForSubtree();
}

scoped_ptr<LayerImpl> LayerImpl::TakeReplicaLayer() {
  replica_layer_id_ = -1;
  return replica_layer_.Pass();
}

ScrollbarLayerImplBase* LayerImpl::ToScrollbarLayer() {
  return NULL;
}

void LayerImpl::SetDrawsContent(bool draws_content) {
  if (draws_content_ == draws_content)
    return;

  draws_content_ = draws_content;
  NoteLayerPropertyChanged();
}

void LayerImpl::SetHideLayerAndSubtree(bool hide) {
  if (hide_layer_and_subtree_ == hide)
    return;

  hide_layer_and_subtree_ = hide;
  NoteLayerPropertyChangedForSubtree();
}

void LayerImpl::SetAnchorPoint(const gfx::PointF& anchor_point) {
  if (anchor_point_ == anchor_point)
    return;

  anchor_point_ = anchor_point;
  NoteLayerPropertyChangedForSubtree();
}

void LayerImpl::SetAnchorPointZ(float anchor_point_z) {
  if (anchor_point_z_ == anchor_point_z)
    return;

  anchor_point_z_ = anchor_point_z;
  NoteLayerPropertyChangedForSubtree();
}

void LayerImpl::SetBackgroundColor(SkColor background_color) {
  if (background_color_ == background_color)
    return;

  background_color_ = background_color;
  NoteLayerPropertyChanged();
}

SkColor LayerImpl::SafeOpaqueBackgroundColor() const {
  SkColor color = background_color();
  if (SkColorGetA(color) == 255 && !contents_opaque()) {
    color = SK_ColorTRANSPARENT;
  } else if (SkColorGetA(color) != 255 && contents_opaque()) {
    for (const LayerImpl* layer = parent(); layer;
         layer = layer->parent()) {
      color = layer->background_color();
      if (SkColorGetA(color) == 255)
        break;
    }
    if (SkColorGetA(color) != 255)
      color = layer_tree_impl()->background_color();
    if (SkColorGetA(color) != 255)
      color = SkColorSetA(color, 255);
  }
  return color;
}

void LayerImpl::SetFilters(const FilterOperations& filters) {
  if (filters_ == filters)
    return;

  filters_ = filters;
  NoteLayerPropertyChangedForSubtree();
}

bool LayerImpl::FilterIsAnimating() const {
  return layer_animation_controller_->IsAnimatingProperty(Animation::Filter);
}

bool LayerImpl::FilterIsAnimatingOnImplOnly() const {
  Animation* filter_animation =
      layer_animation_controller_->GetAnimation(Animation::Filter);
  return filter_animation && filter_animation->is_impl_only();
}

void LayerImpl::SetBackgroundFilters(
    const FilterOperations& filters) {
  if (background_filters_ == filters)
    return;

  background_filters_ = filters;
  NoteLayerPropertyChanged();
}

void LayerImpl::SetMasksToBounds(bool masks_to_bounds) {
  if (masks_to_bounds_ == masks_to_bounds)
    return;

  masks_to_bounds_ = masks_to_bounds;
  NoteLayerPropertyChangedForSubtree();
}

void LayerImpl::SetContentsOpaque(bool opaque) {
  if (contents_opaque_ == opaque)
    return;

  contents_opaque_ = opaque;
  NoteLayerPropertyChangedForSubtree();
}

void LayerImpl::SetOpacity(float opacity) {
  if (opacity_ == opacity)
    return;

  opacity_ = opacity;
  NoteLayerPropertyChangedForSubtree();
}

bool LayerImpl::OpacityIsAnimating() const {
  return layer_animation_controller_->IsAnimatingProperty(Animation::Opacity);
}

bool LayerImpl::OpacityIsAnimatingOnImplOnly() const {
  Animation* opacity_animation =
      layer_animation_controller_->GetAnimation(Animation::Opacity);
  return opacity_animation && opacity_animation->is_impl_only();
}

void LayerImpl::SetBlendMode(SkXfermode::Mode blend_mode) {
  if (blend_mode_ == blend_mode)
    return;

  blend_mode_ = blend_mode;
  NoteLayerPropertyChangedForSubtree();
}

void LayerImpl::SetIsRootForIsolatedGroup(bool root) {
  if (is_root_for_isolated_group_ == root)
    return;

  is_root_for_isolated_group_ = root;
  SetNeedsPushProperties();
}

void LayerImpl::SetPosition(const gfx::PointF& position) {
  if (position_ == position)
    return;

  position_ = position;
  NoteLayerPropertyChangedForSubtree();
}

void LayerImpl::SetShouldFlattenTransform(bool flatten) {
  if (should_flatten_transform_ == flatten)
    return;

  should_flatten_transform_ = flatten;
  NoteLayerPropertyChangedForSubtree();
}

void LayerImpl::SetIs3dSorted(bool sorted) {
  if (is_3d_sorted_ == sorted)
    return;

  is_3d_sorted_ = sorted;
  NoteLayerPropertyChangedForSubtree();
}

void LayerImpl::SetTransform(const gfx::Transform& transform) {
  if (transform_ == transform)
    return;

  transform_ = transform;
  NoteLayerPropertyChangedForSubtree();
}

bool LayerImpl::TransformIsAnimating() const {
  return layer_animation_controller_->IsAnimatingProperty(Animation::Transform);
}

bool LayerImpl::TransformIsAnimatingOnImplOnly() const {
  Animation* transform_animation =
      layer_animation_controller_->GetAnimation(Animation::Transform);
  return transform_animation && transform_animation->is_impl_only();
}

void LayerImpl::SetUpdateRect(const gfx::RectF& update_rect) {
  update_rect_ = update_rect;
  SetNeedsPushProperties();
}

void LayerImpl::SetContentBounds(const gfx::Size& content_bounds) {
  if (this->content_bounds() == content_bounds)
    return;

  draw_properties_.content_bounds = content_bounds;
  NoteLayerPropertyChanged();
}

void LayerImpl::SetContentsScale(float contents_scale_x,
                                 float contents_scale_y) {
  if (this->contents_scale_x() == contents_scale_x &&
      this->contents_scale_y() == contents_scale_y)
    return;

  draw_properties_.contents_scale_x = contents_scale_x;
  draw_properties_.contents_scale_y = contents_scale_y;
  NoteLayerPropertyChanged();
}

void LayerImpl::CalculateContentsScale(
    float ideal_contents_scale,
    float device_scale_factor,
    float page_scale_factor,
    bool animating_transform_to_screen,
    float* contents_scale_x,
    float* contents_scale_y,
    gfx::Size* content_bounds) {
  // Base LayerImpl has all of its content scales and content bounds pushed
  // from its Layer during commit and just reuses those values as-is.
  *contents_scale_x = this->contents_scale_x();
  *contents_scale_y = this->contents_scale_y();
  *content_bounds = this->content_bounds();
}

void LayerImpl::SetScrollOffsetDelegate(
    LayerScrollOffsetDelegate* scroll_offset_delegate) {
  // Having both a scroll parent and a scroll offset delegate is unsupported.
  DCHECK(!scroll_parent_);
  if (!scroll_offset_delegate && scroll_offset_delegate_) {
    scroll_delta_ =
        scroll_offset_delegate_->GetTotalScrollOffset() - scroll_offset_;
  }
  gfx::Vector2dF total_offset = TotalScrollOffset();
  scroll_offset_delegate_ = scroll_offset_delegate;
  if (scroll_offset_delegate_)
    scroll_offset_delegate_->SetTotalScrollOffset(total_offset);
}

bool LayerImpl::IsExternalFlingActive() const {
  return scroll_offset_delegate_ &&
         scroll_offset_delegate_->IsExternalFlingActive();
}

void LayerImpl::SetScrollOffset(const gfx::Vector2d& scroll_offset) {
  SetScrollOffsetAndDelta(scroll_offset, ScrollDelta());
}

void LayerImpl::SetScrollOffsetAndDelta(const gfx::Vector2d& scroll_offset,
                                        const gfx::Vector2dF& scroll_delta) {
  bool changed = false;

  last_scroll_offset_ = scroll_offset;

  if (scroll_offset_ != scroll_offset) {
    changed = true;
    scroll_offset_ = scroll_offset;

    if (scroll_offset_delegate_)
      scroll_offset_delegate_->SetTotalScrollOffset(TotalScrollOffset());
  }

  if (ScrollDelta() != scroll_delta) {
    changed = true;
    if (layer_tree_impl()->IsActiveTree()) {
      LayerImpl* pending_twin =
          layer_tree_impl()->FindPendingTreeLayerById(id());
      if (pending_twin) {
        // The pending twin can't mirror the scroll delta of the active
        // layer.  Although the delta - sent scroll delta difference is
        // identical for both twins, the sent scroll delta for the pending
        // layer is zero, as anything that has been sent has been baked
        // into the layer's position/scroll offset as a part of commit.
        DCHECK(pending_twin->sent_scroll_delta().IsZero());
        pending_twin->SetScrollDelta(scroll_delta - sent_scroll_delta());
      }
    }

    if (scroll_offset_delegate_) {
      scroll_offset_delegate_->SetTotalScrollOffset(scroll_offset_ +
                                                    scroll_delta);
    } else {
      scroll_delta_ = scroll_delta;
    }
  }

  if (changed) {
    NoteLayerPropertyChangedForSubtree();
    ScrollbarParametersDidChange();
  }
}

gfx::Vector2dF LayerImpl::ScrollDelta() const {
  if (scroll_offset_delegate_)
    return scroll_offset_delegate_->GetTotalScrollOffset() - scroll_offset_;
  return scroll_delta_;
}

void LayerImpl::SetScrollDelta(const gfx::Vector2dF& scroll_delta) {
  SetScrollOffsetAndDelta(scroll_offset_, scroll_delta);
}

gfx::Vector2dF LayerImpl::TotalScrollOffset() const {
  return scroll_offset_ + ScrollDelta();
}

void LayerImpl::SetDoubleSided(bool double_sided) {
  if (double_sided_ == double_sided)
    return;

  double_sided_ = double_sided;
  NoteLayerPropertyChangedForSubtree();
}

Region LayerImpl::VisibleContentOpaqueRegion() const {
  if (contents_opaque())
    return visible_content_rect();
  return Region();
}

void LayerImpl::DidBeginTracing() {}

void LayerImpl::ReleaseResources() {}

gfx::Vector2d LayerImpl::MaxScrollOffset() const {
  if (!scroll_clip_layer_ || bounds().IsEmpty())
    return gfx::Vector2d();

  LayerImpl const* page_scale_layer = layer_tree_impl()->page_scale_layer();
  DCHECK(this != page_scale_layer);
  DCHECK(scroll_clip_layer_);
  DCHECK(this != layer_tree_impl()->InnerViewportScrollLayer() ||
         IsContainerForFixedPositionLayers());

  gfx::SizeF scaled_scroll_bounds(bounds());

  float scale_factor = 1.f;
  for (LayerImpl const* current_layer = this;
       current_layer != scroll_clip_layer_;
       current_layer = current_layer->parent()) {
    DCHECK(current_layer);
    float current_layer_scale = 1.f;

    const gfx::Transform& layer_transform = current_layer->transform();
    if (current_layer == page_scale_layer) {
      DCHECK(layer_transform.IsIdentity());
      current_layer_scale = layer_tree_impl()->total_page_scale_factor();
    } else {
      // TODO(wjmaclean) Should we allow for translation too?
      DCHECK(layer_transform.IsScale2d());
      gfx::Vector2dF layer_scale = layer_transform.Scale2d();
      // TODO(wjmaclean) Allow for non-isotropic scales.
      DCHECK(layer_scale.x() == layer_scale.y());
      current_layer_scale = layer_scale.x();
    }

    scale_factor *= current_layer_scale;
  }
  // TODO(wjmaclean) Once we move to a model where the two-viewport model is
  // turned on in all builds, remove the next two lines. For now however, the
  // page scale layer may coincide with the clip layer, and so this is
  // necessary.
  if (page_scale_layer == scroll_clip_layer_)
    scale_factor *= layer_tree_impl()->total_page_scale_factor();

  scaled_scroll_bounds.SetSize(scale_factor * scaled_scroll_bounds.width(),
                               scale_factor * scaled_scroll_bounds.height());

  gfx::Vector2dF max_offset(
      scaled_scroll_bounds.width() - scroll_clip_layer_->bounds().width(),
      scaled_scroll_bounds.height() - scroll_clip_layer_->bounds().height());
  // We need the final scroll offset to be in CSS coords.
  max_offset.Scale(1 / scale_factor);
  max_offset.SetToMax(gfx::Vector2dF());
  return gfx::ToFlooredVector2d(max_offset);
}

gfx::Vector2dF LayerImpl::ClampScrollToMaxScrollOffset() {
  gfx::Vector2dF max_offset = MaxScrollOffset();
  gfx::Vector2dF old_offset = TotalScrollOffset();
  gfx::Vector2dF clamped_offset = old_offset;

  clamped_offset.SetToMin(max_offset);
  clamped_offset.SetToMax(gfx::Vector2d());
  gfx::Vector2dF delta = clamped_offset - old_offset;
  if (!delta.IsZero())
    ScrollBy(delta);

  return delta;
}

void LayerImpl::SetScrollbarPosition(ScrollbarLayerImplBase* scrollbar_layer,
                                     LayerImpl* scrollbar_clip_layer) const {
  DCHECK(scrollbar_layer);
  LayerImpl* page_scale_layer = layer_tree_impl()->page_scale_layer();

  DCHECK(this != page_scale_layer);
  DCHECK(scrollbar_clip_layer);
  DCHECK(this != layer_tree_impl()->InnerViewportScrollLayer() ||
         IsContainerForFixedPositionLayers());
  gfx::RectF clip_rect(gfx::PointF(), scrollbar_clip_layer->bounds());

  // See comment in MaxScrollOffset() regarding the use of the content layer
  // bounds here.
  gfx::RectF scroll_rect(gfx::PointF(), bounds());

  if (scroll_rect.size().IsEmpty())
    return;

  // TODO(wjmaclean) This computation is nearly identical to the one in
  // MaxScrollOffset. Find some way to combine these.
  gfx::Vector2dF current_offset;
  for (LayerImpl const* current_layer = this;
       current_layer != scrollbar_clip_layer;
       current_layer = current_layer->parent()) {
    DCHECK(current_layer);
    const gfx::Transform& layer_transform = current_layer->transform();
    if (current_layer == page_scale_layer) {
      DCHECK(layer_transform.IsIdentity());
      float scale_factor = layer_tree_impl()->total_page_scale_factor();
      current_offset.Scale(scale_factor);
      scroll_rect.Scale(scale_factor);
    } else {
      DCHECK(layer_transform.IsScale2d());
      gfx::Vector2dF layer_scale = layer_transform.Scale2d();
      DCHECK(layer_scale.x() == layer_scale.y());
      gfx::Vector2dF new_offset =
          current_layer->scroll_offset() + current_layer->ScrollDelta();
      new_offset.Scale(layer_scale.x(), layer_scale.y());
      current_offset += new_offset;
    }
  }
  // TODO(wjmaclean) Once we move to a model where the two-viewport model is
  // turned on in all builds, remove the next two lines. For now however, the
  // page scale layer may coincide with the clip layer, and so this is
  // necessary.
  if (page_scale_layer == scrollbar_clip_layer) {
    scroll_rect.Scale(layer_tree_impl()->total_page_scale_factor());
    current_offset.Scale(layer_tree_impl()->total_page_scale_factor());
  }

  scrollbar_layer->SetVerticalAdjust(
      layer_tree_impl()->VerticalAdjust(scrollbar_clip_layer->id()));
  if (scrollbar_layer->orientation() == HORIZONTAL) {
    float visible_ratio = clip_rect.width() / scroll_rect.width();
    scrollbar_layer->SetCurrentPos(current_offset.x());
    scrollbar_layer->SetMaximum(scroll_rect.width() - clip_rect.width());
    scrollbar_layer->SetVisibleToTotalLengthRatio(visible_ratio);
  } else {
    float visible_ratio = clip_rect.height() / scroll_rect.height();
    scrollbar_layer->SetCurrentPos(current_offset.y());
    scrollbar_layer->SetMaximum(scroll_rect.height() - clip_rect.height());
    scrollbar_layer->SetVisibleToTotalLengthRatio(visible_ratio);
  }

  layer_tree_impl()->set_needs_update_draw_properties();
  // TODO(wjmaclean) Should the rest of this function be deleted?
  // TODO(wjmaclean) The scrollbar animator for the pinch-zoom scrollbars should
  // activate for every scroll on the main frame, not just the scrolls that move
  // the pinch virtual viewport (i.e. trigger from either inner or outer
  // viewport).
  if (scrollbar_animation_controller_) {
    bool should_animate = scrollbar_animation_controller_->DidScrollUpdate(
        layer_tree_impl_->CurrentFrameTimeTicks());
    if (should_animate)
      layer_tree_impl_->StartScrollbarAnimation();
  }
}

void LayerImpl::DidBecomeActive() {
  if (layer_tree_impl_->settings().scrollbar_animator ==
      LayerTreeSettings::NoAnimator) {
    return;
  }

  bool need_scrollbar_animation_controller = scrollable() && scrollbars_;
  if (!need_scrollbar_animation_controller) {
    scrollbar_animation_controller_.reset();
    return;
  }

  if (scrollbar_animation_controller_)
    return;

  switch (layer_tree_impl_->settings().scrollbar_animator) {
  case LayerTreeSettings::LinearFade: {
    base::TimeDelta fadeout_delay = base::TimeDelta::FromMilliseconds(
        layer_tree_impl_->settings().scrollbar_linear_fade_delay_ms);
    base::TimeDelta fadeout_length = base::TimeDelta::FromMilliseconds(
        layer_tree_impl_->settings().scrollbar_linear_fade_length_ms);

    scrollbar_animation_controller_ =
        ScrollbarAnimationControllerLinearFade::Create(
            this, fadeout_delay, fadeout_length)
            .PassAs<ScrollbarAnimationController>();
    break;
  }
  case LayerTreeSettings::Thinning: {
    scrollbar_animation_controller_ =
        ScrollbarAnimationControllerThinning::Create(this)
            .PassAs<ScrollbarAnimationController>();
    break;
  }
  case LayerTreeSettings::NoAnimator:
    NOTREACHED();
    break;
  }
}

void LayerImpl::ClearScrollbars() {
  if (!scrollbars_)
    return;

  scrollbars_.reset(NULL);
}

void LayerImpl::AddScrollbar(ScrollbarLayerImplBase* layer) {
  DCHECK(layer);
  DCHECK(!scrollbars_ || scrollbars_->find(layer) == scrollbars_->end());
  if (!scrollbars_)
    scrollbars_.reset(new ScrollbarSet());

  scrollbars_->insert(layer);
}

void LayerImpl::RemoveScrollbar(ScrollbarLayerImplBase* layer) {
  DCHECK(scrollbars_);
  DCHECK(layer);
  DCHECK(scrollbars_->find(layer) != scrollbars_->end());

  scrollbars_->erase(layer);
  if (scrollbars_->empty())
    scrollbars_.reset();
}

bool LayerImpl::HasScrollbar(ScrollbarOrientation orientation) const {
  if (!scrollbars_)
    return false;

  for (ScrollbarSet::iterator it = scrollbars_->begin();
       it != scrollbars_->end();
       ++it)
    if ((*it)->orientation() == orientation)
      return true;

  return false;
}

void LayerImpl::ScrollbarParametersDidChange() {
  if (!scrollbars_)
    return;

  for (ScrollbarSet::iterator it = scrollbars_->begin();
       it != scrollbars_->end();
       ++it)
    (*it)->ScrollbarParametersDidChange();
}

void LayerImpl::SetNeedsPushProperties() {
  if (needs_push_properties_)
    return;
  if (!parent_should_know_need_push_properties() && parent_)
    parent_->AddDependentNeedsPushProperties();
  needs_push_properties_ = true;
}

void LayerImpl::AddDependentNeedsPushProperties() {
  DCHECK_GE(num_dependents_need_push_properties_, 0);

  if (!parent_should_know_need_push_properties() && parent_)
    parent_->AddDependentNeedsPushProperties();

  num_dependents_need_push_properties_++;
}

void LayerImpl::RemoveDependentNeedsPushProperties() {
  num_dependents_need_push_properties_--;
  DCHECK_GE(num_dependents_need_push_properties_, 0);

  if (!parent_should_know_need_push_properties() && parent_)
      parent_->RemoveDependentNeedsPushProperties();
}

void LayerImpl::AsValueInto(base::DictionaryValue* state) const {
  TracedValue::MakeDictIntoImplicitSnapshotWithCategory(
      TRACE_DISABLED_BY_DEFAULT("cc.debug"),
      state,
      "cc::LayerImpl",
      LayerTypeAsString(),
      this);
  state->SetInteger("layer_id", id());
  state->Set("bounds", MathUtil::AsValue(bounds_).release());
  state->Set("position", MathUtil::AsValue(position_).release());
  state->SetInteger("draws_content", DrawsContent());
  state->SetInteger("gpu_memory_usage", GPUMemoryUsageInBytes());
  state->Set("scroll_offset", MathUtil::AsValue(scroll_offset_).release());

  bool clipped;
  gfx::QuadF layer_quad = MathUtil::MapQuad(
      screen_space_transform(),
      gfx::QuadF(gfx::Rect(content_bounds())),
      &clipped);
  state->Set("layer_quad", MathUtil::AsValue(layer_quad).release());

  if (!touch_event_handler_region_.IsEmpty()) {
    state->Set("touch_event_handler_region",
               touch_event_handler_region_.AsValue().release());
  }
  if (have_wheel_event_handlers_) {
    gfx::Rect wheel_rect(content_bounds());
    Region wheel_region(wheel_rect);
    state->Set("wheel_event_handler_region",
               wheel_region.AsValue().release());
  }
  if (have_scroll_event_handlers_) {
    gfx::Rect scroll_rect(content_bounds());
    Region scroll_region(scroll_rect);
    state->Set("scroll_event_handler_region",
               scroll_region.AsValue().release());
  }
  if (!non_fast_scrollable_region_.IsEmpty()) {
    state->Set("non_fast_scrollable_region",
               non_fast_scrollable_region_.AsValue().release());
  }

  scoped_ptr<base::ListValue> children_list(new base::ListValue());
  for (size_t i = 0; i < children_.size(); ++i)
    children_list->Append(children_[i]->AsValue().release());
  state->Set("children", children_list.release());
  if (mask_layer_)
    state->Set("mask_layer", mask_layer_->AsValue().release());
  if (replica_layer_)
    state->Set("replica_layer", replica_layer_->AsValue().release());

  if (scroll_parent_)
    state->SetInteger("scroll_parent", scroll_parent_->id());

  if (clip_parent_)
    state->SetInteger("clip_parent", clip_parent_->id());

  state->SetBoolean("can_use_lcd_text", can_use_lcd_text());
  state->SetBoolean("contents_opaque", contents_opaque());

  state->SetBoolean(
      "has_animation_bounds",
      layer_animation_controller()->HasAnimationThatInflatesBounds());

  gfx::BoxF box;
  if (LayerUtils::GetAnimationBounds(*this, &box))
    state->Set("animation_bounds", MathUtil::AsValue(box).release());

  if (debug_info_.get()) {
    std::string str;
    debug_info_->AppendAsTraceFormat(&str);
    base::JSONReader json_reader;
    scoped_ptr<base::Value> debug_info_value(json_reader.ReadToValue(str));

    if (debug_info_value->IsType(base::Value::TYPE_DICTIONARY)) {
      base::DictionaryValue* dictionary_value = NULL;
      bool converted_to_dictionary =
          debug_info_value->GetAsDictionary(&dictionary_value);
      DCHECK(converted_to_dictionary);
      state->MergeDictionary(dictionary_value);
    } else {
      NOTREACHED();
    }
  }
}

size_t LayerImpl::GPUMemoryUsageInBytes() const { return 0; }

scoped_ptr<base::Value> LayerImpl::AsValue() const {
  scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
  AsValueInto(state.get());
  return state.PassAs<base::Value>();
}

void LayerImpl::RunMicroBenchmark(MicroBenchmarkImpl* benchmark) {
  benchmark->RunOnLayer(this);
}
}  // namespace cc
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root/cc/layers/layer_impl.cc

DEFINITIONS
