root/cc/trees/layer_tree_host_impl.cc

DEFINITIONS

1. DidVisibilityChange
2. GetMaxTransferBufferUsageBytes
3. GetMaxRasterTasksUsageBytes
4. GetMapImageTextureTarget
5. Create
6. OnTimerTick
7. SetActive
8. Active
9. time_source_
10. has_no_damage
11. Create
12. id_
13. BeginMainFrameAborted
14. BeginCommit
15. CommitComplete
16. CanDraw
17. Animate
18. ManageTiles
19. StartPageScaleAnimation
20. ScheduleAnimation
21. HaveTouchEventHandlersAt
22. CreateLatencyInfoSwapPromiseMonitor
23. TrackDamageForAllSurfaces
24. AsValue
25. AppendRenderPass
26. GetDrawMode
27. AppendQuadsForLayer
28. AppendQuadsForRenderSurfaceLayer
29. AppendQuadsToFillScreen
30. CalculateRenderPasses
31. MainThreadHasStoppedFlinging
32. UpdateBackgroundAnimateTicking
33. DidAnimateScrollOffset
34. SetViewportDamage
35. FindRenderPassById
36. RemoveRenderPassesRecursive
37. ShouldRemoveRenderPass
38. RemoveRenderPasses
39. PrepareToDraw
40. EvictTexturesForTesting
41. BlockNotifyReadyToActivateForTesting
42. DidInitializeVisibleTileForTesting
43. EnforceManagedMemoryPolicy
44. UpdateTileManagerMemoryPolicy
45. DidModifyTilePriorities
46. DidInitializeVisibleTile
47. NotifyReadyToActivate
48. SetMemoryPolicy
49. SetTreeActivationCallback
50. SetManagedMemoryPolicy
51. SetExternalDrawConstraints
52. SetNeedsRedrawRect
53. BeginImplFrame
54. DidSwapBuffers
55. OnSwapBuffersComplete
56. ReclaimResources
57. OnCanDrawStateChangedForTree
58. MakeCompositorFrameMetadata
59. LayerTreeHostImplDidBeginTracingCallback
60. DrawLayers
61. DidDrawAllLayers
62. FinishAllRendering
63. IsContextLost
64. GetRendererCapabilities
65. SwapBuffers
66. SetNeedsBeginImplFrame
67. ComputeInnerViewportContainerSize
68. UpdateInnerViewportContainerSize
69. UnscaledScrollableViewportSize
70. VerticalAdjust
71. DidLoseOutputSurface
72. Readback
73. HaveRootScrollLayer
74. RootLayer
75. InnerViewportScrollLayer
76. OuterViewportScrollLayer
77. CurrentlyScrollingLayer
78. IsCurrentlyScrolling
79. FindScrollLayerForContentLayer
80. CreatePendingTree
81. UpdateVisibleTiles
82. ActivatePendingTree
83. SetVisible
84. SetNeedsRedraw
85. ActualManagedMemoryPolicy
86. memory_allocation_limit_bytes
87. memory_allocation_priority_cutoff
88. ReleaseTreeResources
89. CreateAndSetRenderer
90. CreateAndSetTileManager
91. EnforceZeroBudget
92. InitializeRenderer
93. DeferredInitialize
94. ReleaseGL
95. SetViewportSize
96. SetOverdrawBottomHeight
97. SetOverhangUIResource
98. SetDeviceScaleFactor
99. DrawViewportSize
100. DeviceViewport
101. DeviceClip
102. DrawTransform
103. DidChangeTopControlsPosition
104. EnsureRenderSurfaceLayerList
105. BindToClient
106. NextScrollLayer
107. FindScrollLayerForDeviceViewportPoint
108. ScrollBegin
109. ScrollLayerWithViewportSpaceDelta
110. ScrollLayerWithLocalDelta
111. ScrollBy
112. ScrollVerticallyByPage
113. SetRootLayerScrollOffsetDelegate
114. OnRootLayerDelegatedScrollOffsetChanged
115. ClearCurrentlyScrollingLayer
116. ScrollEnd
117. FlingScrollBegin
118. DeviceSpaceDistanceToLayer
119. MouseMoveAt
120. HandleMouseOverScrollbar
121. PinchGestureBegin
122. PinchGestureUpdate
123. PinchGestureEnd
124. CollectScrollDeltas
125. ProcessScrollDeltas
126. SetFullRootLayerDamage
127. ScrollViewportBy
128. AnimatePageScale
129. AnimateTopControls
130. AnimateLayers
131. UpdateAnimationState
132. LowFrequencyAnimationInterval
133. SendReleaseResourcesRecursive
134. SetOffscreenContextProvider
135. LayerTreeAsJson
136. SourceAnimationFrameNumber
137. SendManagedMemoryStats
138. AnimateScrollbars
139. AnimateScrollbarsRecursive
140. StartScrollbarAnimation
141. StartScrollbarAnimationRecursive
142. SetTreePriority
143. UpdateCurrentFrameTime
144. ResetCurrentFrameTimeForNextFrame
145. CurrentFrameTimeTicks
146. AsValueWithFrame
147. ActivationStateAsValue
148. SetDebugState
149. CreateUIResource
150. DeleteUIResource
151. EvictAllUIResources
152. ResourceIdForUIResource
153. IsUIResourceOpaque
154. EvictedUIResourcesExist
155. MarkUIResourceNotEvicted
156. ScheduleMicroBenchmark
157. InsertSwapPromiseMonitor
158. RemoveSwapPromiseMonitor
159. NotifySwapPromiseMonitorsOfSetNeedsRedraw

// Copyright 2011 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/trees/layer_tree_host_impl.h"

#include <algorithm>
#include <limits>

#include "base/basictypes.h"
#include "base/containers/hash_tables.h"
#include "base/json/json_writer.h"
#include "base/metrics/histogram.h"
#include "base/stl_util.h"
#include "base/strings/stringprintf.h"
#include "cc/animation/scrollbar_animation_controller.h"
#include "cc/animation/timing_function.h"
#include "cc/base/latency_info_swap_promise_monitor.h"
#include "cc/base/math_util.h"
#include "cc/base/util.h"
#include "cc/debug/benchmark_instrumentation.h"
#include "cc/debug/debug_rect_history.h"
#include "cc/debug/devtools_instrumentation.h"
#include "cc/debug/frame_rate_counter.h"
#include "cc/debug/paint_time_counter.h"
#include "cc/debug/rendering_stats_instrumentation.h"
#include "cc/debug/traced_value.h"
#include "cc/input/page_scale_animation.h"
#include "cc/input/top_controls_manager.h"
#include "cc/layers/append_quads_data.h"
#include "cc/layers/heads_up_display_layer_impl.h"
#include "cc/layers/layer_impl.h"
#include "cc/layers/layer_iterator.h"
#include "cc/layers/painted_scrollbar_layer_impl.h"
#include "cc/layers/render_surface_impl.h"
#include "cc/layers/scrollbar_layer_impl_base.h"
#include "cc/output/compositor_frame_metadata.h"
#include "cc/output/copy_output_request.h"
#include "cc/output/delegating_renderer.h"
#include "cc/output/gl_renderer.h"
#include "cc/output/software_renderer.h"
#include "cc/quads/render_pass_draw_quad.h"
#include "cc/quads/shared_quad_state.h"
#include "cc/quads/solid_color_draw_quad.h"
#include "cc/quads/texture_draw_quad.h"
#include "cc/resources/memory_history.h"
#include "cc/resources/picture_layer_tiling.h"
#include "cc/resources/prioritized_resource_manager.h"
#include "cc/resources/texture_mailbox_deleter.h"
#include "cc/resources/ui_resource_bitmap.h"
#include "cc/scheduler/delay_based_time_source.h"
#include "cc/trees/damage_tracker.h"
#include "cc/trees/layer_tree_host.h"
#include "cc/trees/layer_tree_host_common.h"
#include "cc/trees/layer_tree_impl.h"
#include "cc/trees/occlusion_tracker.h"
#include "cc/trees/quad_culler.h"
#include "cc/trees/single_thread_proxy.h"
#include "cc/trees/tree_synchronizer.h"
#include "gpu/GLES2/gl2extchromium.h"
#include "ui/gfx/frame_time.h"
#include "ui/gfx/size_conversions.h"
#include "ui/gfx/vector2d_conversions.h"

namespace {

void DidVisibilityChange(cc::LayerTreeHostImpl* id, bool visible) {
  if (visible) {
    TRACE_EVENT_ASYNC_BEGIN1("webkit",
                             "LayerTreeHostImpl::SetVisible",
                             id,
                             "LayerTreeHostImpl",
                             id);
    return;
  }

  TRACE_EVENT_ASYNC_END0("webkit", "LayerTreeHostImpl::SetVisible", id);
}

size_t GetMaxTransferBufferUsageBytes(cc::ContextProvider* context_provider) {
  // Software compositing should not use this value in production. Just use a
  // default value when testing uploads with the software compositor.
  if (!context_provider)
    return std::numeric_limits<size_t>::max();

  // We want to make sure the default transfer buffer size is equal to the
  // amount of data that can be uploaded by the compositor to avoid stalling
  // the pipeline.
  // For reference Chromebook Pixel can upload 1MB in about 0.5ms.
  const size_t kMaxBytesUploadedPerMs = 1024 * 1024 * 2;
  // Assuming a two frame deep pipeline between CPU and GPU and we are
  // drawing 60 frames per second which would require us to draw one
  // frame in 16 milliseconds.
  const size_t kMaxTransferBufferUsageBytes = 16 * 2 * kMaxBytesUploadedPerMs;
  return std::min(
      context_provider->ContextCapabilities().max_transfer_buffer_usage_bytes,
      kMaxTransferBufferUsageBytes);
}

size_t GetMaxRasterTasksUsageBytes(cc::ContextProvider* context_provider) {
  // Transfer-buffer/raster-tasks limits are different but related. We make
  // equal here, as this is ideal when using transfer buffers. When not using
  // transfer buffers we should still limit raster to something similar, to
  // preserve caching behavior (and limit memory waste when priorities change).
  return GetMaxTransferBufferUsageBytes(context_provider);
}

unsigned GetMapImageTextureTarget(cc::ContextProvider* context_provider) {
  if (!context_provider)
    return GL_TEXTURE_2D;

  if (context_provider->ContextCapabilities().gpu.egl_image_external)
    return GL_TEXTURE_EXTERNAL_OES;
  if (context_provider->ContextCapabilities().gpu.texture_rectangle)
    return GL_TEXTURE_RECTANGLE_ARB;

  return GL_TEXTURE_2D;
}

}  // namespace

namespace cc {

class LayerTreeHostImplTimeSourceAdapter : public TimeSourceClient {
 public:
  static scoped_ptr<LayerTreeHostImplTimeSourceAdapter> Create(
      LayerTreeHostImpl* layer_tree_host_impl,
      scoped_refptr<DelayBasedTimeSource> time_source) {
    return make_scoped_ptr(
        new LayerTreeHostImplTimeSourceAdapter(layer_tree_host_impl,
                                               time_source));
  }
  virtual ~LayerTreeHostImplTimeSourceAdapter() {
    time_source_->SetClient(NULL);
    time_source_->SetActive(false);
  }

  virtual void OnTimerTick() OVERRIDE {
    // In single threaded mode we attempt to simulate changing the current
    // thread by maintaining a fake thread id. When we switch from one
    // thread to another, we construct DebugScopedSetXXXThread objects that
    // update the thread id. This lets DCHECKS that ensure we're on the
    // right thread to work correctly in single threaded mode. The problem
    // here is that the timer tasks are run via the message loop, and when
    // they run, we've had no chance to construct a DebugScopedSetXXXThread
    // object. The result is that we report that we're running on the main
    // thread. In multi-threaded mode, this timer is run on the compositor
    // thread, so to keep this consistent in single-threaded mode, we'll
    // construct a DebugScopedSetImplThread object. There is no need to do
    // this in multi-threaded mode since the real thread id's will be
    // correct. In fact, setting fake thread id's interferes with the real
    // thread id's and causes breakage.
    scoped_ptr<DebugScopedSetImplThread> set_impl_thread;
    if (!layer_tree_host_impl_->proxy()->HasImplThread()) {
      set_impl_thread.reset(
          new DebugScopedSetImplThread(layer_tree_host_impl_->proxy()));
    }

    // TODO(enne): This should probably happen post-animate.
    if (layer_tree_host_impl_->pending_tree()) {
      layer_tree_host_impl_->pending_tree()->UpdateDrawProperties();
      layer_tree_host_impl_->ManageTiles();
    }

    layer_tree_host_impl_->Animate(
        layer_tree_host_impl_->CurrentFrameTimeTicks());
    layer_tree_host_impl_->UpdateBackgroundAnimateTicking(true);
    bool start_ready_animations = true;
    layer_tree_host_impl_->UpdateAnimationState(start_ready_animations);
    layer_tree_host_impl_->ResetCurrentFrameTimeForNextFrame();
  }

  void SetActive(bool active) {
    if (active != time_source_->Active())
      time_source_->SetActive(active);
  }

  bool Active() const { return time_source_->Active(); }

 private:
  LayerTreeHostImplTimeSourceAdapter(
      LayerTreeHostImpl* layer_tree_host_impl,
      scoped_refptr<DelayBasedTimeSource> time_source)
      : layer_tree_host_impl_(layer_tree_host_impl),
        time_source_(time_source) {
    time_source_->SetClient(this);
  }

  LayerTreeHostImpl* layer_tree_host_impl_;
  scoped_refptr<DelayBasedTimeSource> time_source_;

  DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImplTimeSourceAdapter);
};

LayerTreeHostImpl::FrameData::FrameData()
    : contains_incomplete_tile(false), has_no_damage(false) {}

LayerTreeHostImpl::FrameData::~FrameData() {}

scoped_ptr<LayerTreeHostImpl> LayerTreeHostImpl::Create(
    const LayerTreeSettings& settings,
    LayerTreeHostImplClient* client,
    Proxy* proxy,
    RenderingStatsInstrumentation* rendering_stats_instrumentation,
    SharedBitmapManager* manager,
    int id) {
  return make_scoped_ptr(new LayerTreeHostImpl(
      settings, client, proxy, rendering_stats_instrumentation, manager, id));
}

LayerTreeHostImpl::LayerTreeHostImpl(
    const LayerTreeSettings& settings,
    LayerTreeHostImplClient* client,
    Proxy* proxy,
    RenderingStatsInstrumentation* rendering_stats_instrumentation,
    SharedBitmapManager* manager,
    int id)
    : client_(client),
      proxy_(proxy),
      input_handler_client_(NULL),
      did_lock_scrolling_layer_(false),
      should_bubble_scrolls_(false),
      wheel_scrolling_(false),
      scroll_affects_scroll_handler_(false),
      scroll_layer_id_when_mouse_over_scrollbar_(0),
      tile_priorities_dirty_(false),
      root_layer_scroll_offset_delegate_(NULL),
      settings_(settings),
      visible_(true),
      cached_managed_memory_policy_(
          PrioritizedResourceManager::DefaultMemoryAllocationLimit(),
          gpu::MemoryAllocation::CUTOFF_ALLOW_EVERYTHING,
          ManagedMemoryPolicy::kDefaultNumResourcesLimit),
      pinch_gesture_active_(false),
      pinch_gesture_end_should_clear_scrolling_layer_(false),
      fps_counter_(FrameRateCounter::Create(proxy_->HasImplThread())),
      paint_time_counter_(PaintTimeCounter::Create()),
      memory_history_(MemoryHistory::Create()),
      debug_rect_history_(DebugRectHistory::Create()),
      texture_mailbox_deleter_(new TextureMailboxDeleter(
          proxy_->HasImplThread() ? proxy_->ImplThreadTaskRunner()
                                  : proxy_->MainThreadTaskRunner())),
      max_memory_needed_bytes_(0),
      last_sent_memory_visible_bytes_(0),
      last_sent_memory_visible_and_nearby_bytes_(0),
      last_sent_memory_use_bytes_(0),
      zero_budget_(false),
      device_scale_factor_(1.f),
      overhang_ui_resource_id_(0),
      overdraw_bottom_height_(0.f),
      device_viewport_valid_for_tile_management_(true),
      external_stencil_test_enabled_(false),
      animation_registrar_(AnimationRegistrar::Create()),
      rendering_stats_instrumentation_(rendering_stats_instrumentation),
      micro_benchmark_controller_(this),
      need_to_update_visible_tiles_before_draw_(false),
#if DCHECK_IS_ON
      did_lose_called_(false),
#endif
      shared_bitmap_manager_(manager),
      id_(id) {
  DCHECK(proxy_->IsImplThread());
  DidVisibilityChange(this, visible_);

  SetDebugState(settings.initial_debug_state);

  if (settings.calculate_top_controls_position) {
    top_controls_manager_ =
        TopControlsManager::Create(this,
                                   settings.top_controls_height,
                                   settings.top_controls_show_threshold,
                                   settings.top_controls_hide_threshold);
  }

  SetDebugState(settings.initial_debug_state);

  // LTHI always has an active tree.
  active_tree_ = LayerTreeImpl::create(this);
  TRACE_EVENT_OBJECT_CREATED_WITH_ID(
      TRACE_DISABLED_BY_DEFAULT("cc.debug"), "cc::LayerTreeHostImpl", this);
}

LayerTreeHostImpl::~LayerTreeHostImpl() {
  DCHECK(proxy_->IsImplThread());
  TRACE_EVENT0("cc", "LayerTreeHostImpl::~LayerTreeHostImpl()");
  TRACE_EVENT_OBJECT_DELETED_WITH_ID(
      TRACE_DISABLED_BY_DEFAULT("cc.debug"), "cc::LayerTreeHostImpl", this);

  if (input_handler_client_) {
    input_handler_client_->WillShutdown();
    input_handler_client_ = NULL;
  }

  // The layer trees must be destroyed before the layer tree host. We've
  // made a contract with our animation controllers that the registrar
  // will outlive them, and we must make good.
  if (recycle_tree_)
    recycle_tree_->Shutdown();
  if (pending_tree_)
    pending_tree_->Shutdown();
  active_tree_->Shutdown();
  recycle_tree_.reset();
  pending_tree_.reset();
  active_tree_.reset();
}

void LayerTreeHostImpl::BeginMainFrameAborted(bool did_handle) {
  // If the begin frame data was handled, then scroll and scale set was applied
  // by the main thread, so the active tree needs to be updated as if these sent
  // values were applied and committed.
  if (did_handle) {
    active_tree_->ApplySentScrollAndScaleDeltasFromAbortedCommit();
    active_tree_->ResetContentsTexturesPurged();
  }
}

void LayerTreeHostImpl::BeginCommit() {}

void LayerTreeHostImpl::CommitComplete() {
  TRACE_EVENT0("cc", "LayerTreeHostImpl::CommitComplete");

  if (settings_.impl_side_painting) {
    // Impl-side painting needs an update immediately post-commit to have the
    // opportunity to create tilings.  Other paths can call UpdateDrawProperties
    // more lazily when needed prior to drawing.
    pending_tree()->ApplyScrollDeltasSinceBeginMainFrame();
    pending_tree_->set_needs_update_draw_properties();
    pending_tree_->UpdateDrawProperties();
    // Start working on newly created tiles immediately if needed.
    if (!tile_manager_ || !tile_priorities_dirty_)
      NotifyReadyToActivate();
    else
      ManageTiles();
  } else {
    active_tree_->set_needs_update_draw_properties();
    if (time_source_client_adapter_ && time_source_client_adapter_->Active())
      DCHECK(active_tree_->root_layer());
  }

  client_->SendManagedMemoryStats();

  micro_benchmark_controller_.DidCompleteCommit();
}

bool LayerTreeHostImpl::CanDraw() const {
  // Note: If you are changing this function or any other function that might
  // affect the result of CanDraw, make sure to call
  // client_->OnCanDrawStateChanged in the proper places and update the
  // NotifyIfCanDrawChanged test.

  if (!renderer_) {
    TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::CanDraw no renderer",
                         TRACE_EVENT_SCOPE_THREAD);
    return false;
  }

  // Must have an OutputSurface if |renderer_| is not NULL.
  DCHECK(output_surface_);

  // TODO(boliu): Make draws without root_layer work and move this below
  // draw_and_swap_full_viewport_every_frame check. Tracked in crbug.com/264967.
  if (!active_tree_->root_layer()) {
    TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::CanDraw no root layer",
                         TRACE_EVENT_SCOPE_THREAD);
    return false;
  }

  if (output_surface_->capabilities().draw_and_swap_full_viewport_every_frame)
    return true;

  if (DrawViewportSize().IsEmpty()) {
    TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::CanDraw empty viewport",
                         TRACE_EVENT_SCOPE_THREAD);
    return false;
  }
  if (active_tree_->ViewportSizeInvalid()) {
    TRACE_EVENT_INSTANT0(
        "cc", "LayerTreeHostImpl::CanDraw viewport size recently changed",
        TRACE_EVENT_SCOPE_THREAD);
    return false;
  }
  if (active_tree_->ContentsTexturesPurged()) {
    TRACE_EVENT_INSTANT0(
        "cc", "LayerTreeHostImpl::CanDraw contents textures purged",
        TRACE_EVENT_SCOPE_THREAD);
    return false;
  }
  if (EvictedUIResourcesExist()) {
    TRACE_EVENT_INSTANT0(
        "cc", "LayerTreeHostImpl::CanDraw UI resources evicted not recreated",
        TRACE_EVENT_SCOPE_THREAD);
    return false;
  }
  return true;
}

void LayerTreeHostImpl::Animate(base::TimeTicks monotonic_time) {
  if (input_handler_client_)
    input_handler_client_->Animate(monotonic_time);
  AnimatePageScale(monotonic_time);
  AnimateLayers(monotonic_time);
  AnimateScrollbars(monotonic_time);
  AnimateTopControls(monotonic_time);
}

void LayerTreeHostImpl::ManageTiles() {
  if (!tile_manager_)
    return;
  if (!tile_priorities_dirty_)
    return;

  tile_priorities_dirty_ = false;
  tile_manager_->ManageTiles(global_tile_state_);

  size_t memory_required_bytes;
  size_t memory_nice_to_have_bytes;
  size_t memory_allocated_bytes;
  size_t memory_used_bytes;
  tile_manager_->GetMemoryStats(&memory_required_bytes,
                                &memory_nice_to_have_bytes,
                                &memory_allocated_bytes,
                                &memory_used_bytes);
  SendManagedMemoryStats(memory_required_bytes,
                         memory_nice_to_have_bytes,
                         memory_used_bytes);

  client_->DidManageTiles();
}

void LayerTreeHostImpl::StartPageScaleAnimation(
    const gfx::Vector2d& target_offset,
    bool anchor_point,
    float page_scale,
    base::TimeDelta duration) {
  if (!InnerViewportScrollLayer())
    return;

  gfx::Vector2dF scroll_total = active_tree_->TotalScrollOffset();
  gfx::SizeF scaled_scrollable_size = active_tree_->ScrollableSize();
  gfx::SizeF viewport_size = UnscaledScrollableViewportSize();

  // Easing constants experimentally determined.
  scoped_ptr<TimingFunction> timing_function =
      CubicBezierTimingFunction::Create(.8, 0, .3, .9).PassAs<TimingFunction>();

  page_scale_animation_ =
      PageScaleAnimation::Create(scroll_total,
                                 active_tree_->total_page_scale_factor(),
                                 viewport_size,
                                 scaled_scrollable_size,
                                 timing_function.Pass());

  if (anchor_point) {
    gfx::Vector2dF anchor(target_offset);
    page_scale_animation_->ZoomWithAnchor(anchor,
                                          page_scale,
                                          duration.InSecondsF());
  } else {
    gfx::Vector2dF scaled_target_offset = target_offset;
    page_scale_animation_->ZoomTo(scaled_target_offset,
                                  page_scale,
                                  duration.InSecondsF());
  }

  SetNeedsRedraw();
  client_->SetNeedsCommitOnImplThread();
  client_->RenewTreePriority();
}

void LayerTreeHostImpl::ScheduleAnimation() {
  SetNeedsRedraw();
}

bool LayerTreeHostImpl::HaveTouchEventHandlersAt(
    const gfx::Point& viewport_point) {
  if (!settings_.touch_hit_testing)
    return true;
  if (!EnsureRenderSurfaceLayerList())
    return false;

  gfx::PointF device_viewport_point =
      gfx::ScalePoint(viewport_point, device_scale_factor_);

  LayerImpl* layer_impl =
      LayerTreeHostCommon::FindLayerThatIsHitByPointInTouchHandlerRegion(
          device_viewport_point,
          active_tree_->RenderSurfaceLayerList());
  return layer_impl != NULL;
}

scoped_ptr<SwapPromiseMonitor>
LayerTreeHostImpl::CreateLatencyInfoSwapPromiseMonitor(
    ui::LatencyInfo* latency) {
  return scoped_ptr<SwapPromiseMonitor>(
      new LatencyInfoSwapPromiseMonitor(latency, NULL, this));
}

void LayerTreeHostImpl::TrackDamageForAllSurfaces(
    LayerImpl* root_draw_layer,
    const LayerImplList& render_surface_layer_list) {
  // For now, we use damage tracking to compute a global scissor. To do this, we
  // must compute all damage tracking before drawing anything, so that we know
  // the root damage rect. The root damage rect is then used to scissor each
  // surface.

  for (int surface_index = render_surface_layer_list.size() - 1;
       surface_index >= 0;
       --surface_index) {
    LayerImpl* render_surface_layer = render_surface_layer_list[surface_index];
    RenderSurfaceImpl* render_surface = render_surface_layer->render_surface();
    DCHECK(render_surface);
    render_surface->damage_tracker()->UpdateDamageTrackingState(
        render_surface->layer_list(),
        render_surface_layer->id(),
        render_surface->SurfacePropertyChangedOnlyFromDescendant(),
        render_surface->content_rect(),
        render_surface_layer->mask_layer(),
        render_surface_layer->filters());
  }
}

scoped_ptr<base::Value> LayerTreeHostImpl::FrameData::AsValue() const {
  scoped_ptr<base::DictionaryValue> value(new base::DictionaryValue());
  value->SetBoolean("contains_incomplete_tile", contains_incomplete_tile);
  value->SetBoolean("has_no_damage", has_no_damage);

  // Quad data can be quite large, so only dump render passes if we select
  // cc.debug.quads.
  bool quads_enabled;
  TRACE_EVENT_CATEGORY_GROUP_ENABLED(
      TRACE_DISABLED_BY_DEFAULT("cc.debug.quads"), &quads_enabled);
  if (quads_enabled) {
    scoped_ptr<base::ListValue> render_pass_list(new base::ListValue());
    for (size_t i = 0; i < render_passes.size(); ++i)
      render_pass_list->Append(render_passes[i]->AsValue().release());
    value->Set("render_passes", render_pass_list.release());
  }
  return value.PassAs<base::Value>();
}

void LayerTreeHostImpl::FrameData::AppendRenderPass(
    scoped_ptr<RenderPass> render_pass) {
  render_passes_by_id[render_pass->id] = render_pass.get();
  render_passes.push_back(render_pass.Pass());
}

static DrawMode GetDrawMode(OutputSurface* output_surface) {
  if (output_surface->ForcedDrawToSoftwareDevice()) {
    return DRAW_MODE_RESOURCELESS_SOFTWARE;
  } else if (output_surface->context_provider()) {
    return DRAW_MODE_HARDWARE;
  } else {
    DCHECK_EQ(!output_surface->software_device(),
              output_surface->capabilities().delegated_rendering);
    return DRAW_MODE_SOFTWARE;
  }
}

static void AppendQuadsForLayer(
    RenderPass* target_render_pass,
    LayerImpl* layer,
    const OcclusionTracker<LayerImpl>& occlusion_tracker,
    AppendQuadsData* append_quads_data) {
  bool for_surface = false;
  QuadCuller quad_culler(&target_render_pass->quad_list,
                         &target_render_pass->shared_quad_state_list,
                         layer,
                         occlusion_tracker,
                         for_surface);
  layer->AppendQuads(&quad_culler, append_quads_data);
}

static void AppendQuadsForRenderSurfaceLayer(
    RenderPass* target_render_pass,
    LayerImpl* layer,
    const RenderPass* contributing_render_pass,
    const OcclusionTracker<LayerImpl>& occlusion_tracker,
    AppendQuadsData* append_quads_data) {
  bool for_surface = true;
  QuadCuller quad_culler(&target_render_pass->quad_list,
                         &target_render_pass->shared_quad_state_list,
                         layer,
                         occlusion_tracker,
                         for_surface);

  bool is_replica = false;
  layer->render_surface()->AppendQuads(&quad_culler,
                                       append_quads_data,
                                       is_replica,
                                       contributing_render_pass->id);

  // Add replica after the surface so that it appears below the surface.
  if (layer->has_replica()) {
    is_replica = true;
    layer->render_surface()->AppendQuads(&quad_culler,
                                         append_quads_data,
                                         is_replica,
                                         contributing_render_pass->id);
  }
}

static void AppendQuadsToFillScreen(
    ResourceProvider::ResourceId overhang_resource_id,
    const gfx::SizeF& overhang_resource_scaled_size,
    const gfx::Rect& root_scroll_layer_rect,
    RenderPass* target_render_pass,
    LayerImpl* root_layer,
    SkColor screen_background_color,
    const OcclusionTracker<LayerImpl>& occlusion_tracker) {
  if (!root_layer || !SkColorGetA(screen_background_color))
    return;

  Region fill_region = occlusion_tracker.ComputeVisibleRegionInScreen();
  if (fill_region.IsEmpty())
    return;

  // Divide the fill region into the part to be filled with the overhang
  // resource and the part to be filled with the background color.
  Region screen_background_color_region = fill_region;
  Region overhang_region;
  if (overhang_resource_id) {
    overhang_region = fill_region;
    overhang_region.Subtract(root_scroll_layer_rect);
    screen_background_color_region.Intersect(root_scroll_layer_rect);
  }

  bool for_surface = false;
  QuadCuller quad_culler(&target_render_pass->quad_list,
                         &target_render_pass->shared_quad_state_list,
                         root_layer,
                         occlusion_tracker,
                         for_surface);

  // Manually create the quad state for the gutter quads, as the root layer
  // doesn't have any bounds and so can't generate this itself.
  // TODO(danakj): Make the gutter quads generated by the solid color layer
  // (make it smarter about generating quads to fill unoccluded areas).

  gfx::Rect root_target_rect = root_layer->render_surface()->content_rect();
  float opacity = 1.f;
  SharedQuadState* shared_quad_state =
      quad_culler.UseSharedQuadState(SharedQuadState::Create());
  shared_quad_state->SetAll(gfx::Transform(),
                            root_target_rect.size(),
                            root_target_rect,
                            root_target_rect,
                            false,
                            opacity,
                            SkXfermode::kSrcOver_Mode);

  for (Region::Iterator fill_rects(screen_background_color_region);
       fill_rects.has_rect();
       fill_rects.next()) {
    gfx::Rect screen_space_rect = fill_rects.rect();
    gfx::Rect visible_screen_space_rect = screen_space_rect;
    // Skip the quad culler and just append the quads directly to avoid
    // occlusion checks.
    scoped_ptr<SolidColorDrawQuad> quad = SolidColorDrawQuad::Create();
    quad->SetNew(shared_quad_state,
                 screen_space_rect,
                 visible_screen_space_rect,
                 screen_background_color,
                 false);
    quad_culler.MaybeAppend(quad.PassAs<DrawQuad>());
  }
  for (Region::Iterator fill_rects(overhang_region);
       fill_rects.has_rect();
       fill_rects.next()) {
    DCHECK(overhang_resource_id);
    gfx::Rect screen_space_rect = fill_rects.rect();
    gfx::Rect opaque_screen_space_rect = screen_space_rect;
    gfx::Rect visible_screen_space_rect = screen_space_rect;
    scoped_ptr<TextureDrawQuad> tex_quad = TextureDrawQuad::Create();
    const float vertex_opacity[4] = {1.f, 1.f, 1.f, 1.f};
    tex_quad->SetNew(
        shared_quad_state,
        screen_space_rect,
        opaque_screen_space_rect,
        visible_screen_space_rect,
        overhang_resource_id,
        false,
        gfx::PointF(
            screen_space_rect.x() / overhang_resource_scaled_size.width(),
            screen_space_rect.y() / overhang_resource_scaled_size.height()),
        gfx::PointF(
            screen_space_rect.right() / overhang_resource_scaled_size.width(),
            screen_space_rect.bottom() /
                overhang_resource_scaled_size.height()),
        screen_background_color,
        vertex_opacity,
        false);
    quad_culler.MaybeAppend(tex_quad.PassAs<DrawQuad>());
  }
}

DrawSwapReadbackResult::DrawResult LayerTreeHostImpl::CalculateRenderPasses(
    FrameData* frame) {
  DCHECK(frame->render_passes.empty());
  DCHECK(CanDraw());
  DCHECK(active_tree_->root_layer());

  TrackDamageForAllSurfaces(active_tree_->root_layer(),
                            *frame->render_surface_layer_list);

  // If the root render surface has no visible damage, then don't generate a
  // frame at all.
  RenderSurfaceImpl* root_surface =
      active_tree_->root_layer()->render_surface();
  bool root_surface_has_no_visible_damage =
      !root_surface->damage_tracker()->current_damage_rect().Intersects(
          root_surface->content_rect());
  bool root_surface_has_contributing_layers =
      !root_surface->layer_list().empty();
  bool hud_wants_to_draw_ = active_tree_->hud_layer() &&
                            active_tree_->hud_layer()->IsAnimatingHUDContents();
  if (root_surface_has_contributing_layers &&
      root_surface_has_no_visible_damage &&
      active_tree_->LayersWithCopyOutputRequest().empty() &&
      !hud_wants_to_draw_) {
    TRACE_EVENT0("cc",
                 "LayerTreeHostImpl::CalculateRenderPasses::EmptyDamageRect");
    frame->has_no_damage = true;
    DCHECK(!output_surface_->capabilities()
               .draw_and_swap_full_viewport_every_frame);
    return DrawSwapReadbackResult::DRAW_SUCCESS;
  }

  TRACE_EVENT1("cc",
               "LayerTreeHostImpl::CalculateRenderPasses",
               "render_surface_layer_list.size()",
               static_cast<uint64>(frame->render_surface_layer_list->size()));

  // Create the render passes in dependency order.
  for (int surface_index = frame->render_surface_layer_list->size() - 1;
       surface_index >= 0;
       --surface_index) {
    LayerImpl* render_surface_layer =
        (*frame->render_surface_layer_list)[surface_index];
    RenderSurfaceImpl* render_surface = render_surface_layer->render_surface();

    bool should_draw_into_render_pass =
        render_surface_layer->parent() == NULL ||
        render_surface->contributes_to_drawn_surface() ||
        render_surface_layer->HasCopyRequest();
    if (should_draw_into_render_pass)
      render_surface_layer->render_surface()->AppendRenderPasses(frame);
  }

  // When we are displaying the HUD, change the root damage rect to cover the
  // entire root surface. This will disable partial-swap/scissor optimizations
  // that would prevent the HUD from updating, since the HUD does not cause
  // damage itself, to prevent it from messing with damage visualizations. Since
  // damage visualizations are done off the LayerImpls and RenderSurfaceImpls,
  // changing the RenderPass does not affect them.
  if (active_tree_->hud_layer()) {
    RenderPass* root_pass = frame->render_passes.back();
    root_pass->damage_rect = root_pass->output_rect;
  }

  OcclusionTracker<LayerImpl> occlusion_tracker(
      active_tree_->root_layer()->render_surface()->content_rect());
  occlusion_tracker.set_minimum_tracking_size(
      settings_.minimum_occlusion_tracking_size);

  if (debug_state_.show_occluding_rects) {
    occlusion_tracker.set_occluding_screen_space_rects_container(
        &frame->occluding_screen_space_rects);
  }
  if (debug_state_.show_non_occluding_rects) {
    occlusion_tracker.set_non_occluding_screen_space_rects_container(
        &frame->non_occluding_screen_space_rects);
  }

  // Add quads to the Render passes in front-to-back order to allow for testing
  // occlusion and performing culling during the tree walk.
  typedef LayerIterator<LayerImpl> LayerIteratorType;

  // Typically when we are missing a texture and use a checkerboard quad, we
  // still draw the frame. However when the layer being checkerboarded is moving
  // due to an impl-animation, we drop the frame to avoid flashing due to the
  // texture suddenly appearing in the future.
  DrawSwapReadbackResult::DrawResult draw_result =
      DrawSwapReadbackResult::DRAW_SUCCESS;
  // When we have a copy request for a layer, we need to draw no matter
  // what, as the layer may disappear after this frame.
  bool have_copy_request = false;

  int layers_drawn = 0;

  const DrawMode draw_mode = GetDrawMode(output_surface_.get());

  LayerIteratorType end =
      LayerIteratorType::End(frame->render_surface_layer_list);
  for (LayerIteratorType it =
           LayerIteratorType::Begin(frame->render_surface_layer_list);
       it != end;
       ++it) {
    RenderPass::Id target_render_pass_id =
        it.target_render_surface_layer()->render_surface()->RenderPassId();
    RenderPass* target_render_pass =
        frame->render_passes_by_id[target_render_pass_id];

    occlusion_tracker.EnterLayer(it);

    AppendQuadsData append_quads_data(target_render_pass_id);

    if (it.represents_target_render_surface()) {
      if (it->HasCopyRequest()) {
        have_copy_request = true;
        it->TakeCopyRequestsAndTransformToTarget(
            &target_render_pass->copy_requests);
      }
    } else if (it.represents_contributing_render_surface() &&
               it->render_surface()->contributes_to_drawn_surface()) {
      RenderPass::Id contributing_render_pass_id =
          it->render_surface()->RenderPassId();
      RenderPass* contributing_render_pass =
          frame->render_passes_by_id[contributing_render_pass_id];
      AppendQuadsForRenderSurfaceLayer(target_render_pass,
                                       *it,
                                       contributing_render_pass,
                                       occlusion_tracker,
                                       &append_quads_data);
    } else if (it.represents_itself() && it->DrawsContent() &&
               !it->visible_content_rect().IsEmpty()) {
      bool occluded = occlusion_tracker.Occluded(it->render_target(),
                                                 it->visible_content_rect(),
                                                 it->draw_transform());
      if (!occluded && it->WillDraw(draw_mode, resource_provider_.get())) {
        DCHECK_EQ(active_tree_, it->layer_tree_impl());

        frame->will_draw_layers.push_back(*it);

        if (it->HasContributingDelegatedRenderPasses()) {
          RenderPass::Id contributing_render_pass_id =
              it->FirstContributingRenderPassId();
          while (frame->render_passes_by_id.find(contributing_render_pass_id) !=
                 frame->render_passes_by_id.end()) {
            RenderPass* render_pass =
                frame->render_passes_by_id[contributing_render_pass_id];

            AppendQuadsData append_quads_data(render_pass->id);
            AppendQuadsForLayer(render_pass,
                                *it,
                                occlusion_tracker,
                                &append_quads_data);

            contributing_render_pass_id =
                it->NextContributingRenderPassId(contributing_render_pass_id);
          }
        }

        AppendQuadsForLayer(target_render_pass,
                            *it,
                            occlusion_tracker,
                            &append_quads_data);
      }

      ++layers_drawn;
    }

    if (append_quads_data.num_missing_tiles) {
      bool layer_has_animating_transform =
          it->screen_space_transform_is_animating() ||
          it->draw_transform_is_animating();
      if (layer_has_animating_transform) {
        draw_result =
            DrawSwapReadbackResult::DRAW_ABORTED_CHECKERBOARD_ANIMATIONS;
      }
    }

    if (append_quads_data.had_incomplete_tile) {
      frame->contains_incomplete_tile = true;
      if (active_tree()->RequiresHighResToDraw())
        draw_result =
            DrawSwapReadbackResult::DRAW_ABORTED_MISSING_HIGH_RES_CONTENT;
    }

    occlusion_tracker.LeaveLayer(it);
  }

  if (have_copy_request ||
      output_surface_->capabilities().draw_and_swap_full_viewport_every_frame)
    draw_result = DrawSwapReadbackResult::DRAW_SUCCESS;

#if DCHECK_IS_ON
  for (size_t i = 0; i < frame->render_passes.size(); ++i) {
    for (size_t j = 0; j < frame->render_passes[i]->quad_list.size(); ++j)
      DCHECK(frame->render_passes[i]->quad_list[j]->shared_quad_state);
    DCHECK(frame->render_passes_by_id.find(frame->render_passes[i]->id)
           != frame->render_passes_by_id.end());
  }
#endif
  DCHECK(frame->render_passes.back()->output_rect.origin().IsOrigin());

  if (!active_tree_->has_transparent_background()) {
    frame->render_passes.back()->has_transparent_background = false;
    AppendQuadsToFillScreen(
        ResourceIdForUIResource(overhang_ui_resource_id_),
        gfx::ScaleSize(overhang_ui_resource_size_, device_scale_factor_),
        active_tree_->RootScrollLayerDeviceViewportBounds(),
        frame->render_passes.back(),
        active_tree_->root_layer(),
        active_tree_->background_color(),
        occlusion_tracker);
  }

  RemoveRenderPasses(CullRenderPassesWithNoQuads(), frame);
  renderer_->DecideRenderPassAllocationsForFrame(frame->render_passes);

  // Any copy requests left in the tree are not going to get serviced, and
  // should be aborted.
  ScopedPtrVector<CopyOutputRequest> requests_to_abort;
  while (!active_tree_->LayersWithCopyOutputRequest().empty()) {
    LayerImpl* layer = active_tree_->LayersWithCopyOutputRequest().back();
    layer->TakeCopyRequestsAndTransformToTarget(&requests_to_abort);
  }
  for (size_t i = 0; i < requests_to_abort.size(); ++i)
    requests_to_abort[i]->SendEmptyResult();

  // If we're making a frame to draw, it better have at least one render pass.
  DCHECK(!frame->render_passes.empty());

  // Should only have one render pass in resourceless software mode.
  if (output_surface_->ForcedDrawToSoftwareDevice())
    DCHECK_EQ(1u, frame->render_passes.size());

  return draw_result;
}

void LayerTreeHostImpl::MainThreadHasStoppedFlinging() {
  if (input_handler_client_)
    input_handler_client_->MainThreadHasStoppedFlinging();
}

void LayerTreeHostImpl::UpdateBackgroundAnimateTicking(
    bool should_background_tick) {
  DCHECK(proxy_->IsImplThread());
  if (should_background_tick)
    DCHECK(active_tree_->root_layer());

  bool enabled = should_background_tick && needs_animate_layers();

  // Lazily create the time_source adapter so that we can vary the interval for
  // testing.
  if (!time_source_client_adapter_) {
    time_source_client_adapter_ = LayerTreeHostImplTimeSourceAdapter::Create(
        this,
        DelayBasedTimeSource::Create(
            LowFrequencyAnimationInterval(),
            proxy_->HasImplThread() ? proxy_->ImplThreadTaskRunner()
                                    : proxy_->MainThreadTaskRunner()));
  }

  time_source_client_adapter_->SetActive(enabled);
}

void LayerTreeHostImpl::DidAnimateScrollOffset() {
  client_->SetNeedsCommitOnImplThread();
  client_->RenewTreePriority();
}

void LayerTreeHostImpl::SetViewportDamage(const gfx::Rect& damage_rect) {
  viewport_damage_rect_.Union(damage_rect);
}

static inline RenderPass* FindRenderPassById(
    RenderPass::Id render_pass_id,
    const LayerTreeHostImpl::FrameData& frame) {
  RenderPassIdHashMap::const_iterator it =
      frame.render_passes_by_id.find(render_pass_id);
  return it != frame.render_passes_by_id.end() ? it->second : NULL;
}

static void RemoveRenderPassesRecursive(RenderPass::Id remove_render_pass_id,
                                        LayerTreeHostImpl::FrameData* frame) {
  RenderPass* remove_render_pass =
      FindRenderPassById(remove_render_pass_id, *frame);
  // The pass was already removed by another quad - probably the original, and
  // we are the replica.
  if (!remove_render_pass)
    return;
  RenderPassList& render_passes = frame->render_passes;
  RenderPassList::iterator to_remove = std::find(render_passes.begin(),
                                                 render_passes.end(),
                                                 remove_render_pass);

  DCHECK(to_remove != render_passes.end());

  scoped_ptr<RenderPass> removed_pass = render_passes.take(to_remove);
  frame->render_passes.erase(to_remove);
  frame->render_passes_by_id.erase(remove_render_pass_id);

  // Now follow up for all RenderPass quads and remove their RenderPasses
  // recursively.
  const QuadList& quad_list = removed_pass->quad_list;
  QuadList::ConstBackToFrontIterator quad_list_iterator =
      quad_list.BackToFrontBegin();
  for (; quad_list_iterator != quad_list.BackToFrontEnd();
       ++quad_list_iterator) {
    DrawQuad* current_quad = (*quad_list_iterator);
    if (current_quad->material != DrawQuad::RENDER_PASS)
      continue;

    RenderPass::Id next_remove_render_pass_id =
        RenderPassDrawQuad::MaterialCast(current_quad)->render_pass_id;
    RemoveRenderPassesRecursive(next_remove_render_pass_id, frame);
  }
}

bool LayerTreeHostImpl::CullRenderPassesWithNoQuads::ShouldRemoveRenderPass(
    const RenderPassDrawQuad& quad, const FrameData& frame) const {
  const RenderPass* render_pass =
      FindRenderPassById(quad.render_pass_id, frame);
  if (!render_pass)
    return false;

  // If any quad or RenderPass draws into this RenderPass, then keep it.
  const QuadList& quad_list = render_pass->quad_list;
  for (QuadList::ConstBackToFrontIterator quad_list_iterator =
           quad_list.BackToFrontBegin();
       quad_list_iterator != quad_list.BackToFrontEnd();
       ++quad_list_iterator) {
    DrawQuad* current_quad = *quad_list_iterator;

    if (current_quad->material != DrawQuad::RENDER_PASS)
      return false;

    const RenderPass* contributing_pass = FindRenderPassById(
        RenderPassDrawQuad::MaterialCast(current_quad)->render_pass_id, frame);
    if (contributing_pass)
      return false;
  }
  return true;
}

// Defined for linking tests.
template CC_EXPORT void LayerTreeHostImpl::RemoveRenderPasses<
  LayerTreeHostImpl::CullRenderPassesWithNoQuads>(
      CullRenderPassesWithNoQuads culler, FrameData*);

// static
template <typename RenderPassCuller>
void LayerTreeHostImpl::RemoveRenderPasses(RenderPassCuller culler,
                                           FrameData* frame) {
  for (size_t it = culler.RenderPassListBegin(frame->render_passes);
       it != culler.RenderPassListEnd(frame->render_passes);
       it = culler.RenderPassListNext(it)) {
    const RenderPass* current_pass = frame->render_passes[it];
    const QuadList& quad_list = current_pass->quad_list;
    QuadList::ConstBackToFrontIterator quad_list_iterator =
        quad_list.BackToFrontBegin();

    for (; quad_list_iterator != quad_list.BackToFrontEnd();
         ++quad_list_iterator) {
      DrawQuad* current_quad = *quad_list_iterator;

      if (current_quad->material != DrawQuad::RENDER_PASS)
        continue;

      const RenderPassDrawQuad* render_pass_quad =
          RenderPassDrawQuad::MaterialCast(current_quad);
      if (!culler.ShouldRemoveRenderPass(*render_pass_quad, *frame))
        continue;

      // We are changing the vector in the middle of iteration. Because we
      // delete render passes that draw into the current pass, we are
      // guaranteed that any data from the iterator to the end will not
      // change. So, capture the iterator position from the end of the
      // list, and restore it after the change.
      size_t position_from_end = frame->render_passes.size() - it;
      RemoveRenderPassesRecursive(render_pass_quad->render_pass_id, frame);
      it = frame->render_passes.size() - position_from_end;
      DCHECK_GE(frame->render_passes.size(), position_from_end);
    }
  }
}

DrawSwapReadbackResult::DrawResult LayerTreeHostImpl::PrepareToDraw(
    FrameData* frame,
    const gfx::Rect& damage_rect) {
  TRACE_EVENT1("cc",
               "LayerTreeHostImpl::PrepareToDraw",
               "SourceFrameNumber",
               active_tree_->source_frame_number());

  if (need_to_update_visible_tiles_before_draw_ &&
      tile_manager_ && tile_manager_->UpdateVisibleTiles()) {
    DidInitializeVisibleTile();
  }
  need_to_update_visible_tiles_before_draw_ = true;

  active_tree_->UpdateDrawProperties();

  frame->render_surface_layer_list = &active_tree_->RenderSurfaceLayerList();
  frame->render_passes.clear();
  frame->render_passes_by_id.clear();
  frame->will_draw_layers.clear();
  frame->contains_incomplete_tile = false;
  frame->has_no_damage = false;

  gfx::Rect device_viewport_damage_rect(damage_rect);
  if (active_tree_->root_layer()) {
    device_viewport_damage_rect.Union(viewport_damage_rect_);
    viewport_damage_rect_ = gfx::Rect();

    active_tree_->root_layer()->render_surface()->damage_tracker()->
        AddDamageNextUpdate(device_viewport_damage_rect);
  }

  DrawSwapReadbackResult::DrawResult draw_result = CalculateRenderPasses(frame);
  if (draw_result != DrawSwapReadbackResult::DRAW_SUCCESS) {
    DCHECK(!output_surface_->capabilities()
               .draw_and_swap_full_viewport_every_frame);
    return draw_result;
  }

  // If we return DRAW_SUCCESS, then we expect DrawLayers() to be called before
  // this function is called again.
  return draw_result;
}

void LayerTreeHostImpl::EvictTexturesForTesting() {
  EnforceManagedMemoryPolicy(ManagedMemoryPolicy(0));
}

void LayerTreeHostImpl::BlockNotifyReadyToActivateForTesting(bool block) {
  NOTREACHED();
}

void LayerTreeHostImpl::DidInitializeVisibleTileForTesting() {
  DidInitializeVisibleTile();
}

void LayerTreeHostImpl::EnforceManagedMemoryPolicy(
    const ManagedMemoryPolicy& policy) {

  bool evicted_resources = client_->ReduceContentsTextureMemoryOnImplThread(
      visible_ ? policy.bytes_limit_when_visible : 0,
      ManagedMemoryPolicy::PriorityCutoffToValue(
          visible_ ? policy.priority_cutoff_when_visible
                   : gpu::MemoryAllocation::CUTOFF_ALLOW_NOTHING));
  if (evicted_resources) {
    active_tree_->SetContentsTexturesPurged();
    if (pending_tree_)
      pending_tree_->SetContentsTexturesPurged();
    client_->SetNeedsCommitOnImplThread();
    client_->OnCanDrawStateChanged(CanDraw());
    client_->RenewTreePriority();
  }
  client_->SendManagedMemoryStats();

  UpdateTileManagerMemoryPolicy(policy);
}

void LayerTreeHostImpl::UpdateTileManagerMemoryPolicy(
    const ManagedMemoryPolicy& policy) {
  if (!tile_manager_)
    return;

  // TODO(reveman): We should avoid keeping around unused resources if
  // possible. crbug.com/224475
  global_tile_state_.hard_memory_limit_in_bytes = 0;
  global_tile_state_.soft_memory_limit_in_bytes = 0;
  if (visible_ && policy.bytes_limit_when_visible > 0) {
    global_tile_state_.hard_memory_limit_in_bytes =
        policy.bytes_limit_when_visible;
    global_tile_state_.soft_memory_limit_in_bytes =
        (static_cast<int64>(global_tile_state_.hard_memory_limit_in_bytes) *
         settings_.max_memory_for_prepaint_percentage) /
        100;
  }
  // Unused limit is calculated from soft-limit, as hard-limit may
  // be very high and shouldn't typically be exceeded.
  global_tile_state_.unused_memory_limit_in_bytes = static_cast<size_t>(
      (static_cast<int64>(global_tile_state_.soft_memory_limit_in_bytes) *
       settings_.max_unused_resource_memory_percentage) /
      100);
  global_tile_state_.memory_limit_policy =
      ManagedMemoryPolicy::PriorityCutoffToTileMemoryLimitPolicy(
          visible_ ?
          policy.priority_cutoff_when_visible :
          gpu::MemoryAllocation::CUTOFF_ALLOW_NOTHING);
  global_tile_state_.num_resources_limit = policy.num_resources_limit;

  DidModifyTilePriorities();
}

void LayerTreeHostImpl::DidModifyTilePriorities() {
  DCHECK(settings_.impl_side_painting);
  // Mark priorities as dirty and schedule a ManageTiles().
  tile_priorities_dirty_ = true;
  client_->SetNeedsManageTilesOnImplThread();
}

void LayerTreeHostImpl::DidInitializeVisibleTile() {
  // TODO(reveman): Determine tiles that changed and only damage
  // what's necessary.
  SetFullRootLayerDamage();
  if (client_ && !client_->IsInsideDraw())
    client_->DidInitializeVisibleTileOnImplThread();
}

void LayerTreeHostImpl::NotifyReadyToActivate() {
  client_->NotifyReadyToActivate();
}

void LayerTreeHostImpl::SetMemoryPolicy(const ManagedMemoryPolicy& policy) {
  SetManagedMemoryPolicy(policy, zero_budget_);
}

void LayerTreeHostImpl::SetTreeActivationCallback(
    const base::Closure& callback) {
  DCHECK(proxy_->IsImplThread());
  DCHECK(settings_.impl_side_painting || callback.is_null());
  tree_activation_callback_ = callback;
}

void LayerTreeHostImpl::SetManagedMemoryPolicy(
    const ManagedMemoryPolicy& policy, bool zero_budget) {
  if (cached_managed_memory_policy_ == policy && zero_budget_ == zero_budget)
    return;

  ManagedMemoryPolicy old_policy = ActualManagedMemoryPolicy();

  cached_managed_memory_policy_ = policy;
  zero_budget_ = zero_budget;
  ManagedMemoryPolicy actual_policy = ActualManagedMemoryPolicy();

  if (old_policy == actual_policy)
    return;

  if (!proxy_->HasImplThread()) {
    // In single-thread mode, this can be called on the main thread by
    // GLRenderer::OnMemoryAllocationChanged.
    DebugScopedSetImplThread impl_thread(proxy_);
    EnforceManagedMemoryPolicy(actual_policy);
  } else {
    DCHECK(proxy_->IsImplThread());
    EnforceManagedMemoryPolicy(actual_policy);
  }

  // If there is already enough memory to draw everything imaginable and the
  // new memory limit does not change this, then do not re-commit. Don't bother
  // skipping commits if this is not visible (commits don't happen when not
  // visible, there will almost always be a commit when this becomes visible).
  bool needs_commit = true;
  if (visible() &&
      actual_policy.bytes_limit_when_visible >= max_memory_needed_bytes_ &&
      old_policy.bytes_limit_when_visible >= max_memory_needed_bytes_ &&
      actual_policy.priority_cutoff_when_visible ==
          old_policy.priority_cutoff_when_visible) {
    needs_commit = false;
  }

  if (needs_commit)
    client_->SetNeedsCommitOnImplThread();
}

void LayerTreeHostImpl::SetExternalDrawConstraints(
    const gfx::Transform& transform,
    const gfx::Rect& viewport,
    const gfx::Rect& clip,
    bool valid_for_tile_management) {
  external_transform_ = transform;
  external_viewport_ = viewport;
  external_clip_ = clip;
  device_viewport_valid_for_tile_management_ = valid_for_tile_management;
}

void LayerTreeHostImpl::SetNeedsRedrawRect(const gfx::Rect& damage_rect) {
  if (damage_rect.IsEmpty())
    return;
  NotifySwapPromiseMonitorsOfSetNeedsRedraw();
  client_->SetNeedsRedrawRectOnImplThread(damage_rect);
}

void LayerTreeHostImpl::BeginImplFrame(const BeginFrameArgs& args) {
  client_->BeginImplFrame(args);
}

void LayerTreeHostImpl::DidSwapBuffers() {
  client_->DidSwapBuffersOnImplThread();
}

void LayerTreeHostImpl::OnSwapBuffersComplete() {
  client_->OnSwapBuffersCompleteOnImplThread();
}

void LayerTreeHostImpl::ReclaimResources(const CompositorFrameAck* ack) {
  // TODO(piman): We may need to do some validation on this ack before
  // processing it.
  if (renderer_)
    renderer_->ReceiveSwapBuffersAck(*ack);

  // In OOM, we now might be able to release more resources that were held
  // because they were exported.
  if (tile_manager_) {
    DCHECK(tile_manager_->resource_pool());

    // TODO(vmpstr): Move resource pool to be LTHI member.
    tile_manager_->resource_pool()->CheckBusyResources();
    tile_manager_->resource_pool()->ReduceResourceUsage();
  }
}

void LayerTreeHostImpl::OnCanDrawStateChangedForTree() {
  client_->OnCanDrawStateChanged(CanDraw());
}

CompositorFrameMetadata LayerTreeHostImpl::MakeCompositorFrameMetadata() const {
  CompositorFrameMetadata metadata;
  metadata.device_scale_factor = device_scale_factor_;
  metadata.page_scale_factor = active_tree_->total_page_scale_factor();
  metadata.viewport_size = active_tree_->ScrollableViewportSize();
  metadata.root_layer_size = active_tree_->ScrollableSize();
  metadata.min_page_scale_factor = active_tree_->min_page_scale_factor();
  metadata.max_page_scale_factor = active_tree_->max_page_scale_factor();
  if (top_controls_manager_) {
    metadata.location_bar_offset =
        gfx::Vector2dF(0.f, top_controls_manager_->controls_top_offset());
    metadata.location_bar_content_translation =
        gfx::Vector2dF(0.f, top_controls_manager_->content_top_offset());
    metadata.overdraw_bottom_height = overdraw_bottom_height_;
  }

  if (!InnerViewportScrollLayer())
    return metadata;

  metadata.root_scroll_offset = active_tree_->TotalScrollOffset();

  return metadata;
}

static void LayerTreeHostImplDidBeginTracingCallback(LayerImpl* layer) {
  layer->DidBeginTracing();
}

void LayerTreeHostImpl::DrawLayers(FrameData* frame,
                                   base::TimeTicks frame_begin_time) {
  TRACE_EVENT0("cc", "LayerTreeHostImpl::DrawLayers");
  DCHECK(CanDraw());

  if (frame->has_no_damage) {
    TRACE_EVENT_INSTANT0("cc", "EarlyOut_NoDamage", TRACE_EVENT_SCOPE_THREAD);
    DCHECK(!output_surface_->capabilities()
               .draw_and_swap_full_viewport_every_frame);
    return;
  }

  DCHECK(!frame->render_passes.empty());

  fps_counter_->SaveTimeStamp(frame_begin_time,
                              !output_surface_->context_provider());
  bool on_main_thread = false;
  rendering_stats_instrumentation_->IncrementFrameCount(
      1, on_main_thread);

  if (tile_manager_) {
    memory_history_->SaveEntry(
        tile_manager_->memory_stats_from_last_assign());
  }

  if (debug_state_.ShowHudRects()) {
    debug_rect_history_->SaveDebugRectsForCurrentFrame(
        active_tree_->root_layer(),
        active_tree_->hud_layer(),
        *frame->render_surface_layer_list,
        frame->occluding_screen_space_rects,
        frame->non_occluding_screen_space_rects,
        debug_state_);
  }

  if (!settings_.impl_side_painting && debug_state_.continuous_painting) {
    const RenderingStats& stats =
        rendering_stats_instrumentation_->GetRenderingStats();
    paint_time_counter_->SavePaintTime(stats.main_stats.paint_time);
  }

  bool is_new_trace;
  TRACE_EVENT_IS_NEW_TRACE(&is_new_trace);
  if (is_new_trace) {
    if (pending_tree_) {
      LayerTreeHostCommon::CallFunctionForSubtree(
          pending_tree_->root_layer(),
          base::Bind(&LayerTreeHostImplDidBeginTracingCallback));
    }
    LayerTreeHostCommon::CallFunctionForSubtree(
        active_tree_->root_layer(),
        base::Bind(&LayerTreeHostImplDidBeginTracingCallback));
  }

  TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(
      TRACE_DISABLED_BY_DEFAULT("cc.debug") ","
      TRACE_DISABLED_BY_DEFAULT("cc.debug.quads"), "cc::LayerTreeHostImpl",
      this, TracedValue::FromValue(AsValueWithFrame(frame).release()));

  // Because the contents of the HUD depend on everything else in the frame, the
  // contents of its texture are updated as the last thing before the frame is
  // drawn.
  if (active_tree_->hud_layer()) {
    TRACE_EVENT0("cc", "DrawLayers.UpdateHudTexture");
    active_tree_->hud_layer()->UpdateHudTexture(
        GetDrawMode(output_surface_.get()), resource_provider_.get());
  }

  if (output_surface_->ForcedDrawToSoftwareDevice()) {
    bool disable_picture_quad_image_filtering =
        IsCurrentlyScrolling() || needs_animate_layers();

    scoped_ptr<SoftwareRenderer> temp_software_renderer =
        SoftwareRenderer::Create(this, &settings_, output_surface_.get(), NULL);
    temp_software_renderer->DrawFrame(&frame->render_passes,
                                      NULL,
                                      device_scale_factor_,
                                      DeviceViewport(),
                                      DeviceClip(),
                                      disable_picture_quad_image_filtering);
  } else {
    renderer_->DrawFrame(&frame->render_passes,
                         offscreen_context_provider_.get(),
                         device_scale_factor_,
                         DeviceViewport(),
                         DeviceClip(),
                         false);
  }
  // The render passes should be consumed by the renderer.
  DCHECK(frame->render_passes.empty());
  frame->render_passes_by_id.clear();

  // The next frame should start by assuming nothing has changed, and changes
  // are noted as they occur.
  // TODO(boliu): If we did a temporary software renderer frame, propogate the
  // damage forward to the next frame.
  for (size_t i = 0; i < frame->render_surface_layer_list->size(); i++) {
    (*frame->render_surface_layer_list)[i]->render_surface()->damage_tracker()->
        DidDrawDamagedArea();
  }
  active_tree_->root_layer()->ResetAllChangeTrackingForSubtree();

  devtools_instrumentation::DidDrawFrame(id_);
  BenchmarkInstrumentation::IssueImplThreadRenderingStatsEvent(
      rendering_stats_instrumentation_->impl_thread_rendering_stats());
  rendering_stats_instrumentation_->AccumulateAndClearImplThreadStats();
}

void LayerTreeHostImpl::DidDrawAllLayers(const FrameData& frame) {
  for (size_t i = 0; i < frame.will_draw_layers.size(); ++i)
    frame.will_draw_layers[i]->DidDraw(resource_provider_.get());

  // Once all layers have been drawn, pending texture uploads should no
  // longer block future uploads.
  resource_provider_->MarkPendingUploadsAsNonBlocking();
}

void LayerTreeHostImpl::FinishAllRendering() {
  if (renderer_)
    renderer_->Finish();
}

bool LayerTreeHostImpl::IsContextLost() {
  DCHECK(proxy_->IsImplThread());
  return renderer_ && renderer_->IsContextLost();
}

const RendererCapabilitiesImpl&
LayerTreeHostImpl::GetRendererCapabilities() const {
  return renderer_->Capabilities();
}

bool LayerTreeHostImpl::SwapBuffers(const LayerTreeHostImpl::FrameData& frame) {
  active_tree()->ResetRequiresHighResToDraw();
  if (frame.has_no_damage) {
    active_tree()->BreakSwapPromises(SwapPromise::SWAP_FAILS);
    return false;
  }
  CompositorFrameMetadata metadata = MakeCompositorFrameMetadata();
  active_tree()->FinishSwapPromises(&metadata);
  for (size_t i = 0; i < metadata.latency_info.size(); i++) {
    TRACE_EVENT_FLOW_STEP0(
        "input",
        "LatencyInfo.Flow",
        TRACE_ID_DONT_MANGLE(metadata.latency_info[i].trace_id),
        "SwapBuffers");
  }
  renderer_->SwapBuffers(metadata);
  return true;
}

void LayerTreeHostImpl::SetNeedsBeginImplFrame(bool enable) {
  if (output_surface_)
    output_surface_->SetNeedsBeginImplFrame(enable);
}

gfx::SizeF LayerTreeHostImpl::ComputeInnerViewportContainerSize() const {
  gfx::SizeF dip_size =
      gfx::ScaleSize(device_viewport_size_, 1.f / device_scale_factor());

  float top_offset =
      top_controls_manager_ ? top_controls_manager_->content_top_offset() : 0.f;

  return gfx::SizeF(dip_size.width(),
                    dip_size.height() - top_offset - overdraw_bottom_height_);
}

void LayerTreeHostImpl::UpdateInnerViewportContainerSize() {
  LayerImpl* container_layer = active_tree_->InnerViewportContainerLayer();
  if (!container_layer)
    return;

  // We pass the value returned from UnscaledScrollableViewportSize() here as
  // it accounts for scrollbar dimensions when
  // container_layer->masks_to_bounds() is set.
  container_layer->SetTemporaryImplBounds(UnscaledScrollableViewportSize());
}

gfx::SizeF LayerTreeHostImpl::UnscaledScrollableViewportSize() const {
  // Use the root container layer bounds if it clips to them, otherwise, the
  // true viewport size should be used.
  LayerImpl* container_layer = active_tree_->InnerViewportContainerLayer();
  if (container_layer && container_layer->masks_to_bounds()) {
    DCHECK(!top_controls_manager_);
    DCHECK_EQ(0, overdraw_bottom_height_);
    return container_layer->bounds();
  }

  return ComputeInnerViewportContainerSize();
}

float LayerTreeHostImpl::VerticalAdjust() const {
  if (!active_tree_->InnerViewportContainerLayer())
    return 0;

  return active_tree_->InnerViewportContainerLayer()->BoundsDelta().y();
}

void LayerTreeHostImpl::DidLoseOutputSurface() {
  if (resource_provider_)
    resource_provider_->DidLoseOutputSurface();
  // TODO(jamesr): The renderer_ check is needed to make some of the
  // LayerTreeHostContextTest tests pass, but shouldn't be necessary (or
  // important) in production. We should adjust the test to not need this.
  if (renderer_)
    client_->DidLoseOutputSurfaceOnImplThread();
#if DCHECK_IS_ON
  did_lose_called_ = true;
#endif
}

void LayerTreeHostImpl::Readback(void* pixels,
                                 const gfx::Rect& rect_in_device_viewport) {
  DCHECK(renderer_);
  renderer_->GetFramebufferPixels(pixels, rect_in_device_viewport);
}

bool LayerTreeHostImpl::HaveRootScrollLayer() const {
  return !!InnerViewportScrollLayer();
}

LayerImpl* LayerTreeHostImpl::RootLayer() const {
  return active_tree_->root_layer();
}

LayerImpl* LayerTreeHostImpl::InnerViewportScrollLayer() const {
  return active_tree_->InnerViewportScrollLayer();
}

LayerImpl* LayerTreeHostImpl::OuterViewportScrollLayer() const {
  return active_tree_->OuterViewportScrollLayer();
}

LayerImpl* LayerTreeHostImpl::CurrentlyScrollingLayer() const {
  return active_tree_->CurrentlyScrollingLayer();
}

bool LayerTreeHostImpl::IsCurrentlyScrolling() const {
  return CurrentlyScrollingLayer() ||
         (InnerViewportScrollLayer() &&
          InnerViewportScrollLayer()->IsExternalFlingActive()) ||
         (OuterViewportScrollLayer() &&
          OuterViewportScrollLayer()->IsExternalFlingActive());
}

// Content layers can be either directly scrollable or contained in an outer
// scrolling layer which applies the scroll transform. Given a content layer,
// this function returns the associated scroll layer if any.
static LayerImpl* FindScrollLayerForContentLayer(LayerImpl* layer_impl) {
  if (!layer_impl)
    return NULL;

  if (layer_impl->scrollable())
    return layer_impl;

  if (layer_impl->DrawsContent() &&
      layer_impl->parent() &&
      layer_impl->parent()->scrollable())
    return layer_impl->parent();

  return NULL;
}

void LayerTreeHostImpl::CreatePendingTree() {
  CHECK(!pending_tree_);
  if (recycle_tree_)
    recycle_tree_.swap(pending_tree_);
  else
    pending_tree_ = LayerTreeImpl::create(this);
  client_->OnCanDrawStateChanged(CanDraw());
  TRACE_EVENT_ASYNC_BEGIN0("cc", "PendingTree:waiting", pending_tree_.get());
}

void LayerTreeHostImpl::UpdateVisibleTiles() {
  if (tile_manager_ && tile_manager_->UpdateVisibleTiles())
    DidInitializeVisibleTile();
  need_to_update_visible_tiles_before_draw_ = false;
}

void LayerTreeHostImpl::ActivatePendingTree() {
  CHECK(pending_tree_);
  TRACE_EVENT_ASYNC_END0("cc", "PendingTree:waiting", pending_tree_.get());

  need_to_update_visible_tiles_before_draw_ = true;

  active_tree_->SetRootLayerScrollOffsetDelegate(NULL);
  active_tree_->PushPersistedState(pending_tree_.get());
  if (pending_tree_->needs_full_tree_sync()) {
    active_tree_->SetRootLayer(
        TreeSynchronizer::SynchronizeTrees(pending_tree_->root_layer(),
                                           active_tree_->DetachLayerTree(),
                                           active_tree_.get()));
  }
  TreeSynchronizer::PushProperties(pending_tree_->root_layer(),
                                   active_tree_->root_layer());
  DCHECK(!recycle_tree_);

  // Process any requests in the UI resource queue.  The request queue is given
  // in LayerTreeHost::FinishCommitOnImplThread.  This must take place before
  // the swap.
  pending_tree_->ProcessUIResourceRequestQueue();

  pending_tree_->PushPropertiesTo(active_tree_.get());

  // Now that we've synced everything from the pending tree to the active
  // tree, rename the pending tree the recycle tree so we can reuse it on the
  // next sync.
  pending_tree_.swap(recycle_tree_);

  active_tree_->DidBecomeActive();
  active_tree_->SetRootLayerScrollOffsetDelegate(
      root_layer_scroll_offset_delegate_);

  client_->OnCanDrawStateChanged(CanDraw());
  SetNeedsRedraw();
  client_->RenewTreePriority();

  if (debug_state_.continuous_painting) {
    const RenderingStats& stats =
        rendering_stats_instrumentation_->GetRenderingStats();
    paint_time_counter_->SavePaintTime(stats.main_stats.paint_time +
                                       stats.main_stats.record_time +
                                       stats.impl_stats.rasterize_time);
  }

  UpdateInnerViewportContainerSize();
  client_->DidActivatePendingTree();
  if (!tree_activation_callback_.is_null())
    tree_activation_callback_.Run();

  if (time_source_client_adapter_ && time_source_client_adapter_->Active())
    DCHECK(active_tree_->root_layer());
  devtools_instrumentation::DidActivateLayerTree(
      id_, active_tree_->source_frame_number());
}

void LayerTreeHostImpl::SetVisible(bool visible) {
  DCHECK(proxy_->IsImplThread());

  if (visible_ == visible)
    return;
  visible_ = visible;
  DidVisibilityChange(this, visible_);
  EnforceManagedMemoryPolicy(ActualManagedMemoryPolicy());

  if (!visible_) {
    active_tree()->SetRequiresHighResToDraw();
    EvictAllUIResources();
  }

  // Evict tiles immediately if invisible since this tab may never get another
  // draw or timer tick.
  if (!visible_)
    ManageTiles();

  if (!renderer_)
    return;

  renderer_->SetVisible(visible);
}

void LayerTreeHostImpl::SetNeedsRedraw() {
  NotifySwapPromiseMonitorsOfSetNeedsRedraw();
  client_->SetNeedsRedrawOnImplThread();
}

ManagedMemoryPolicy LayerTreeHostImpl::ActualManagedMemoryPolicy() const {
  ManagedMemoryPolicy actual = cached_managed_memory_policy_;
  // TODO(ernstm): The second condition disables pre-painting for all layers
  // when GPU rasterization is enabled. Once we selectively enable GPU
  // rasterization per layer, we also need to disable pre-painting selectively:
  // crbug.com/335387
  if (debug_state_.rasterize_only_visible_content ||
      settings_.rasterization_site == LayerTreeSettings::GpuRasterization) {
    actual.priority_cutoff_when_visible =
        gpu::MemoryAllocation::CUTOFF_ALLOW_REQUIRED_ONLY;
  }

  if (zero_budget_) {
    actual.bytes_limit_when_visible = 0;
  }

  return actual;
}

size_t LayerTreeHostImpl::memory_allocation_limit_bytes() const {
  return ActualManagedMemoryPolicy().bytes_limit_when_visible;
}

int LayerTreeHostImpl::memory_allocation_priority_cutoff() const {
  return ManagedMemoryPolicy::PriorityCutoffToValue(
      ActualManagedMemoryPolicy().priority_cutoff_when_visible);
}

void LayerTreeHostImpl::ReleaseTreeResources() {
  if (active_tree_->root_layer())
    SendReleaseResourcesRecursive(active_tree_->root_layer());
  if (pending_tree_ && pending_tree_->root_layer())
    SendReleaseResourcesRecursive(pending_tree_->root_layer());
  if (recycle_tree_ && recycle_tree_->root_layer())
    SendReleaseResourcesRecursive(recycle_tree_->root_layer());

  EvictAllUIResources();
}

void LayerTreeHostImpl::CreateAndSetRenderer(
    OutputSurface* output_surface,
    ResourceProvider* resource_provider,
    bool skip_gl_renderer) {
  DCHECK(!renderer_);
  if (output_surface->capabilities().delegated_rendering) {
    renderer_ = DelegatingRenderer::Create(
        this, &settings_, output_surface, resource_provider);
  } else if (output_surface->context_provider() && !skip_gl_renderer) {
    renderer_ = GLRenderer::Create(this,
                                   &settings_,
                                   output_surface,
                                   resource_provider,
                                   texture_mailbox_deleter_.get(),
                                   settings_.highp_threshold_min);
  } else if (output_surface->software_device()) {
    renderer_ = SoftwareRenderer::Create(
        this, &settings_, output_surface, resource_provider);
  }

  if (renderer_) {
    renderer_->SetVisible(visible_);
    SetFullRootLayerDamage();

    // See note in LayerTreeImpl::UpdateDrawProperties.  Renderer needs to be
    // initialized to get max texture size.  Also, after releasing resources,
    // trees need another update to generate new ones.
    active_tree_->set_needs_update_draw_properties();
    if (pending_tree_)
      pending_tree_->set_needs_update_draw_properties();
    client_->UpdateRendererCapabilitiesOnImplThread();
  }
}

void LayerTreeHostImpl::CreateAndSetTileManager(
    ResourceProvider* resource_provider,
    ContextProvider* context_provider,
    bool using_map_image,
    bool allow_rasterize_on_demand) {
  DCHECK(settings_.impl_side_painting);
  DCHECK(resource_provider);
  DCHECK(proxy_->ImplThreadTaskRunner());
  tile_manager_ =
      TileManager::Create(this,
                          proxy_->ImplThreadTaskRunner(),
                          resource_provider,
                          context_provider,
                          rendering_stats_instrumentation_,
                          using_map_image,
                          allow_rasterize_on_demand,
                          GetMaxTransferBufferUsageBytes(context_provider),
                          GetMaxRasterTasksUsageBytes(context_provider),
                          GetMapImageTextureTarget(context_provider));

  UpdateTileManagerMemoryPolicy(ActualManagedMemoryPolicy());
  need_to_update_visible_tiles_before_draw_ = false;
}

void LayerTreeHostImpl::EnforceZeroBudget(bool zero_budget) {
  SetManagedMemoryPolicy(cached_managed_memory_policy_, zero_budget);
}

bool LayerTreeHostImpl::InitializeRenderer(
    scoped_ptr<OutputSurface> output_surface) {
#if DCHECK_IS_ON
  DCHECK(!renderer_ || did_lose_called_);
#endif

  // Since we will create a new resource provider, we cannot continue to use
  // the old resources (i.e. render_surfaces and texture IDs). Clear them
  // before we destroy the old resource provider.
  ReleaseTreeResources();

  // Note: order is important here.
  renderer_.reset();
  tile_manager_.reset();
  resource_provider_.reset();
  output_surface_.reset();

  if (!output_surface->BindToClient(this))
    return false;

  scoped_ptr<ResourceProvider> resource_provider =
      ResourceProvider::Create(output_surface.get(),
                               shared_bitmap_manager_,
                               settings_.highp_threshold_min,
                               settings_.use_rgba_4444_textures,
                               settings_.texture_id_allocation_chunk_size);
  if (!resource_provider)
    return false;

  if (output_surface->capabilities().deferred_gl_initialization)
    EnforceZeroBudget(true);

  bool skip_gl_renderer = false;
  CreateAndSetRenderer(
      output_surface.get(), resource_provider.get(), skip_gl_renderer);

  if (!renderer_)
    return false;

  if (settings_.impl_side_painting) {
    CreateAndSetTileManager(
        resource_provider.get(),
        output_surface->context_provider().get(),
        GetRendererCapabilities().using_map_image,
        GetRendererCapabilities().allow_rasterize_on_demand);
  }

  // Setup BeginImplFrameEmulation if it's not supported natively
  if (!settings_.begin_impl_frame_scheduling_enabled) {
    const base::TimeDelta display_refresh_interval =
      base::TimeDelta::FromMicroseconds(
          base::Time::kMicrosecondsPerSecond /
          settings_.refresh_rate);

    output_surface->InitializeBeginImplFrameEmulation(
        proxy_->ImplThreadTaskRunner(),
        settings_.throttle_frame_production,
        display_refresh_interval);
  }

  int max_frames_pending =
      output_surface->capabilities().max_frames_pending;
  if (max_frames_pending <= 0)
    max_frames_pending = OutputSurface::DEFAULT_MAX_FRAMES_PENDING;
  output_surface->SetMaxFramesPending(max_frames_pending);

  resource_provider_ = resource_provider.Pass();
  output_surface_ = output_surface.Pass();

  client_->OnCanDrawStateChanged(CanDraw());

  return true;
}

bool LayerTreeHostImpl::DeferredInitialize(
    scoped_refptr<ContextProvider> offscreen_context_provider) {
  DCHECK(output_surface_->capabilities().deferred_gl_initialization);
  DCHECK(settings_.impl_side_painting);
  DCHECK(output_surface_->context_provider());

  ReleaseTreeResources();
  renderer_.reset();

  bool resource_provider_success = resource_provider_->InitializeGL();

  bool success = resource_provider_success;
  if (success) {
    bool skip_gl_renderer = false;
    CreateAndSetRenderer(
        output_surface_.get(), resource_provider_.get(), skip_gl_renderer);
    if (!renderer_)
      success = false;
  }

  if (success) {
    if (offscreen_context_provider.get() &&
        !offscreen_context_provider->BindToCurrentThread())
      success = false;
  }

  if (success) {
    EnforceZeroBudget(false);
    client_->SetNeedsCommitOnImplThread();
  } else {
    if (offscreen_context_provider.get()) {
      if (offscreen_context_provider->BindToCurrentThread())
        offscreen_context_provider->VerifyContexts();
      offscreen_context_provider = NULL;
    }

    client_->DidLoseOutputSurfaceOnImplThread();

    if (resource_provider_success) {
      // If this fails the context provider will be dropped from the output
      // surface and destroyed. But the GLRenderer expects the output surface
      // to stick around - and hold onto the context3d - as long as it is alive.
      // TODO(danakj): Remove the need for this code path: crbug.com/276411
      renderer_.reset();

      // The resource provider can't stay in GL mode or it tries to clean up GL
      // stuff, but the context provider is going away on the output surface
      // which contradicts being in GL mode.
      // TODO(danakj): Remove the need for this code path: crbug.com/276411
      resource_provider_->InitializeSoftware();
    }
  }

  SetOffscreenContextProvider(offscreen_context_provider);
  return success;
}

void LayerTreeHostImpl::ReleaseGL() {
  DCHECK(output_surface_->capabilities().deferred_gl_initialization);
  DCHECK(settings_.impl_side_painting);
  DCHECK(output_surface_->context_provider());

  ReleaseTreeResources();
  renderer_.reset();
  tile_manager_.reset();
  resource_provider_->InitializeSoftware();

  bool skip_gl_renderer = true;
  CreateAndSetRenderer(
      output_surface_.get(), resource_provider_.get(), skip_gl_renderer);
  DCHECK(renderer_);

  EnforceZeroBudget(true);
  CreateAndSetTileManager(resource_provider_.get(),
                          NULL,
                          GetRendererCapabilities().using_map_image,
                          GetRendererCapabilities().allow_rasterize_on_demand);
  DCHECK(tile_manager_);

  SetOffscreenContextProvider(NULL);

  client_->SetNeedsCommitOnImplThread();
}

void LayerTreeHostImpl::SetViewportSize(const gfx::Size& device_viewport_size) {
  if (device_viewport_size == device_viewport_size_)
    return;

  if (pending_tree_)
    active_tree_->SetViewportSizeInvalid();

  device_viewport_size_ = device_viewport_size;

  UpdateInnerViewportContainerSize();
  client_->OnCanDrawStateChanged(CanDraw());
  SetFullRootLayerDamage();
}

void LayerTreeHostImpl::SetOverdrawBottomHeight(float overdraw_bottom_height) {
  if (overdraw_bottom_height == overdraw_bottom_height_)
    return;
  overdraw_bottom_height_ = overdraw_bottom_height;

  UpdateInnerViewportContainerSize();
  SetFullRootLayerDamage();
}

void LayerTreeHostImpl::SetOverhangUIResource(
    UIResourceId overhang_ui_resource_id,
    const gfx::Size& overhang_ui_resource_size) {
  overhang_ui_resource_id_ = overhang_ui_resource_id;
  overhang_ui_resource_size_ = overhang_ui_resource_size;
}

void LayerTreeHostImpl::SetDeviceScaleFactor(float device_scale_factor) {
  if (device_scale_factor == device_scale_factor_)
    return;
  device_scale_factor_ = device_scale_factor;

  UpdateInnerViewportContainerSize();
  SetFullRootLayerDamage();
}

gfx::Size LayerTreeHostImpl::DrawViewportSize() const {
  return DeviceViewport().size();
}

gfx::Rect LayerTreeHostImpl::DeviceViewport() const {
  if (external_viewport_.IsEmpty())
    return gfx::Rect(device_viewport_size_);

  return external_viewport_;
}

gfx::Rect LayerTreeHostImpl::DeviceClip() const {
  if (external_clip_.IsEmpty())
    return DeviceViewport();

  return external_clip_;
}

const gfx::Transform& LayerTreeHostImpl::DrawTransform() const {
  return external_transform_;
}

void LayerTreeHostImpl::DidChangeTopControlsPosition() {
  UpdateInnerViewportContainerSize();
  SetNeedsRedraw();
  active_tree_->set_needs_update_draw_properties();
  SetFullRootLayerDamage();
}

bool LayerTreeHostImpl::EnsureRenderSurfaceLayerList() {
  active_tree_->UpdateDrawProperties();
  return !active_tree_->RenderSurfaceLayerList().empty();
}

void LayerTreeHostImpl::BindToClient(InputHandlerClient* client) {
  DCHECK(input_handler_client_ == NULL);
  input_handler_client_ = client;
}

static LayerImpl* NextScrollLayer(LayerImpl* layer) {
  if (LayerImpl* scroll_parent = layer->scroll_parent())
    return scroll_parent;
  return layer->parent();
}

LayerImpl* LayerTreeHostImpl::FindScrollLayerForDeviceViewportPoint(
    const gfx::PointF& device_viewport_point,
    InputHandler::ScrollInputType type,
    LayerImpl* layer_impl,
    bool* scroll_on_main_thread,
    bool* has_ancestor_scroll_handler) const {
  DCHECK(scroll_on_main_thread);

  // Walk up the hierarchy and look for a scrollable layer.
  LayerImpl* potentially_scrolling_layer_impl = 0;
  for (; layer_impl; layer_impl = NextScrollLayer(layer_impl)) {
    // The content layer can also block attempts to scroll outside the main
    // thread.
    ScrollStatus status = layer_impl->TryScroll(device_viewport_point, type);
    if (status == ScrollOnMainThread) {
      *scroll_on_main_thread = true;
      return NULL;
    }

    LayerImpl* scroll_layer_impl = FindScrollLayerForContentLayer(layer_impl);
    if (!scroll_layer_impl)
      continue;

    status = scroll_layer_impl->TryScroll(device_viewport_point, type);
    // If any layer wants to divert the scroll event to the main thread, abort.
    if (status == ScrollOnMainThread) {
      *scroll_on_main_thread = true;
      return NULL;
    }

    if (has_ancestor_scroll_handler &&
        scroll_layer_impl->have_scroll_event_handlers())
      *has_ancestor_scroll_handler = true;

    if (status == ScrollStarted && !potentially_scrolling_layer_impl)
      potentially_scrolling_layer_impl = scroll_layer_impl;
  }

  return potentially_scrolling_layer_impl;
}

InputHandler::ScrollStatus LayerTreeHostImpl::ScrollBegin(
    const gfx::Point& viewport_point,
    InputHandler::ScrollInputType type) {
  TRACE_EVENT0("cc", "LayerTreeHostImpl::ScrollBegin");

  if (top_controls_manager_)
    top_controls_manager_->ScrollBegin();

  DCHECK(!CurrentlyScrollingLayer());
  ClearCurrentlyScrollingLayer();

  if (!EnsureRenderSurfaceLayerList())
    return ScrollIgnored;

  gfx::PointF device_viewport_point = gfx::ScalePoint(viewport_point,
                                                      device_scale_factor_);
  LayerImpl* layer_impl = LayerTreeHostCommon::FindLayerThatIsHitByPoint(
      device_viewport_point,
      active_tree_->RenderSurfaceLayerList());
  bool scroll_on_main_thread = false;
  LayerImpl* potentially_scrolling_layer_impl =
      FindScrollLayerForDeviceViewportPoint(device_viewport_point,
                                            type,
                                            layer_impl,
                                            &scroll_on_main_thread,
                                            &scroll_affects_scroll_handler_);

  if (scroll_on_main_thread) {
    UMA_HISTOGRAM_BOOLEAN("TryScroll.SlowScroll", true);
    return ScrollOnMainThread;
  }

  // If we want to send a DidOverscroll for this scroll it can't be ignored.
  if (!potentially_scrolling_layer_impl)
    potentially_scrolling_layer_impl = OuterViewportScrollLayer()
                                           ? OuterViewportScrollLayer()
                                           : InnerViewportScrollLayer();

  if (potentially_scrolling_layer_impl) {
    active_tree_->SetCurrentlyScrollingLayer(
        potentially_scrolling_layer_impl);
    should_bubble_scrolls_ = (type != NonBubblingGesture);
    wheel_scrolling_ = (type == Wheel);
    client_->RenewTreePriority();
    UMA_HISTOGRAM_BOOLEAN("TryScroll.SlowScroll", false);
    return ScrollStarted;
  }
  return ScrollIgnored;
}

gfx::Vector2dF LayerTreeHostImpl::ScrollLayerWithViewportSpaceDelta(
    LayerImpl* layer_impl,
    float scale_from_viewport_to_screen_space,
    const gfx::PointF& viewport_point,
    const gfx::Vector2dF& viewport_delta) {
  // Layers with non-invertible screen space transforms should not have passed
  // the scroll hit test in the first place.
  DCHECK(layer_impl->screen_space_transform().IsInvertible());
  gfx::Transform inverse_screen_space_transform(
      gfx::Transform::kSkipInitialization);
  bool did_invert = layer_impl->screen_space_transform().GetInverse(
      &inverse_screen_space_transform);
  // TODO(shawnsingh): With the advent of impl-side crolling for non-root
  // layers, we may need to explicitly handle uninvertible transforms here.
  DCHECK(did_invert);

  gfx::PointF screen_space_point =
      gfx::ScalePoint(viewport_point, scale_from_viewport_to_screen_space);

  gfx::Vector2dF screen_space_delta = viewport_delta;
  screen_space_delta.Scale(scale_from_viewport_to_screen_space);

  // First project the scroll start and end points to local layer space to find
  // the scroll delta in layer coordinates.
  bool start_clipped, end_clipped;
  gfx::PointF screen_space_end_point = screen_space_point + screen_space_delta;
  gfx::PointF local_start_point =
      MathUtil::ProjectPoint(inverse_screen_space_transform,
                             screen_space_point,
                             &start_clipped);
  gfx::PointF local_end_point =
      MathUtil::ProjectPoint(inverse_screen_space_transform,
                             screen_space_end_point,
                             &end_clipped);

  // In general scroll point coordinates should not get clipped.
  DCHECK(!start_clipped);
  DCHECK(!end_clipped);
  if (start_clipped || end_clipped)
    return gfx::Vector2dF();

  // local_start_point and local_end_point are in content space but we want to
  // move them to layer space for scrolling.
  float width_scale = 1.f / layer_impl->contents_scale_x();
  float height_scale = 1.f / layer_impl->contents_scale_y();
  local_start_point.Scale(width_scale, height_scale);
  local_end_point.Scale(width_scale, height_scale);

  // Apply the scroll delta.
  gfx::Vector2dF previous_delta = layer_impl->ScrollDelta();
  layer_impl->ScrollBy(local_end_point - local_start_point);

  // Get the end point in the layer's content space so we can apply its
  // ScreenSpaceTransform.
  gfx::PointF actual_local_end_point = local_start_point +
                                       layer_impl->ScrollDelta() -
                                       previous_delta;
  gfx::PointF actual_local_content_end_point =
      gfx::ScalePoint(actual_local_end_point,
                      1.f / width_scale,
                      1.f / height_scale);

  // Calculate the applied scroll delta in viewport space coordinates.
  gfx::PointF actual_screen_space_end_point =
      MathUtil::MapPoint(layer_impl->screen_space_transform(),
                         actual_local_content_end_point,
                         &end_clipped);
  DCHECK(!end_clipped);
  if (end_clipped)
    return gfx::Vector2dF();
  gfx::PointF actual_viewport_end_point =
      gfx::ScalePoint(actual_screen_space_end_point,
                      1.f / scale_from_viewport_to_screen_space);
  return actual_viewport_end_point - viewport_point;
}

static gfx::Vector2dF ScrollLayerWithLocalDelta(LayerImpl* layer_impl,
    const gfx::Vector2dF& local_delta) {
  gfx::Vector2dF previous_delta(layer_impl->ScrollDelta());
  layer_impl->ScrollBy(local_delta);
  return layer_impl->ScrollDelta() - previous_delta;
}

bool LayerTreeHostImpl::ScrollBy(const gfx::Point& viewport_point,
                                 const gfx::Vector2dF& scroll_delta) {
  TRACE_EVENT0("cc", "LayerTreeHostImpl::ScrollBy");
  if (!CurrentlyScrollingLayer())
    return false;

  gfx::Vector2dF pending_delta = scroll_delta;
  gfx::Vector2dF unused_root_delta;
  bool did_scroll_x = false;
  bool did_scroll_y = false;
  bool did_scroll_top_controls = false;
  // TODO(wjmaclean) Should we guard against CurrentlyScrollingLayer() == 0
  // here?
  bool consume_by_top_controls =
      top_controls_manager_ &&
      (((CurrentlyScrollingLayer() == InnerViewportScrollLayer() ||
         CurrentlyScrollingLayer() == OuterViewportScrollLayer()) &&
        InnerViewportScrollLayer()->MaxScrollOffset().y() > 0) ||
       scroll_delta.y() < 0);

  for (LayerImpl* layer_impl = CurrentlyScrollingLayer();
       layer_impl;
       layer_impl = layer_impl->parent()) {
    if (!layer_impl->scrollable())
      continue;

    if (layer_impl == InnerViewportScrollLayer()) {
      // Only allow bubble scrolling when the scroll is in the direction to make
      // the top controls visible.
      gfx::Vector2dF applied_delta;
      gfx::Vector2dF excess_delta;
      if (consume_by_top_controls) {
        excess_delta = top_controls_manager_->ScrollBy(pending_delta);
        applied_delta = pending_delta - excess_delta;
        pending_delta = excess_delta;
        // Force updating of vertical adjust values if needed.
        if (applied_delta.y() != 0) {
          did_scroll_top_controls = true;
          layer_impl->ScrollbarParametersDidChange();
        }
      }
      // Track root layer deltas for reporting overscroll.
      unused_root_delta = pending_delta;
    }

    gfx::Vector2dF applied_delta;
    // Gesture events need to be transformed from viewport coordinates to local
    // layer coordinates so that the scrolling contents exactly follow the
    // user's finger. In contrast, wheel events represent a fixed amount of
    // scrolling so we can just apply them directly.
    if (!wheel_scrolling_) {
      float scale_from_viewport_to_screen_space = device_scale_factor_;
      applied_delta =
          ScrollLayerWithViewportSpaceDelta(layer_impl,
                                            scale_from_viewport_to_screen_space,
                                            viewport_point, pending_delta);
    } else {
      applied_delta = ScrollLayerWithLocalDelta(layer_impl, pending_delta);
    }

    const float kEpsilon = 0.1f;
    if (layer_impl == InnerViewportScrollLayer()) {
      unused_root_delta.Subtract(applied_delta);
      if (std::abs(unused_root_delta.x()) < kEpsilon)
        unused_root_delta.set_x(0.0f);
      if (std::abs(unused_root_delta.y()) < kEpsilon)
        unused_root_delta.set_y(0.0f);
    }

    // If the layer wasn't able to move, try the next one in the hierarchy.
    bool did_move_layer_x = std::abs(applied_delta.x()) > kEpsilon;
    bool did_move_layer_y = std::abs(applied_delta.y()) > kEpsilon;
    did_scroll_x |= did_move_layer_x;
    did_scroll_y |= did_move_layer_y;
    if (!did_move_layer_x && !did_move_layer_y) {
      // Scrolls should always bubble between the outer and inner viewports
      if (should_bubble_scrolls_ || !did_lock_scrolling_layer_ ||
          layer_impl == OuterViewportScrollLayer())
        continue;
      else
        break;
    }

    did_lock_scrolling_layer_ = true;
    if (!should_bubble_scrolls_) {
      active_tree_->SetCurrentlyScrollingLayer(layer_impl);
      break;
    }

    // If the applied delta is within 45 degrees of the input delta, bail out to
    // make it easier to scroll just one layer in one direction without
    // affecting any of its parents.
    float angle_threshold = 45;
    if (MathUtil::SmallestAngleBetweenVectors(
            applied_delta, pending_delta) < angle_threshold) {
      pending_delta = gfx::Vector2d();
      break;
    }

    // Allow further movement only on an axis perpendicular to the direction in
    // which the layer moved.
    gfx::Vector2dF perpendicular_axis(-applied_delta.y(), applied_delta.x());
    pending_delta = MathUtil::ProjectVector(pending_delta, perpendicular_axis);

    if (gfx::ToRoundedVector2d(pending_delta).IsZero())
      break;
  }

  bool did_scroll_content = did_scroll_x || did_scroll_y;
  if (did_scroll_content) {
    client_->SetNeedsCommitOnImplThread();
    SetNeedsRedraw();
    client_->RenewTreePriority();
  }

  // Scrolling along an axis resets accumulated root overscroll for that axis.
  if (did_scroll_x)
    accumulated_root_overscroll_.set_x(0);
  if (did_scroll_y)
    accumulated_root_overscroll_.set_y(0);

  accumulated_root_overscroll_ += unused_root_delta;
  bool did_overscroll = !unused_root_delta.IsZero();
  if (did_overscroll && input_handler_client_) {
    input_handler_client_->DidOverscroll(accumulated_root_overscroll_,
                                         unused_root_delta);
  }

  return did_scroll_content || did_scroll_top_controls;
}

// This implements scrolling by page as described here:
// http://msdn.microsoft.com/en-us/library/windows/desktop/ms645601(v=vs.85).aspx#_win32_The_Mouse_Wheel
// for events with WHEEL_PAGESCROLL set.
bool LayerTreeHostImpl::ScrollVerticallyByPage(const gfx::Point& viewport_point,
                                               ScrollDirection direction) {
  DCHECK(wheel_scrolling_);

  for (LayerImpl* layer_impl = CurrentlyScrollingLayer();
       layer_impl;
       layer_impl = layer_impl->parent()) {
    if (!layer_impl->scrollable())
      continue;

    if (!layer_impl->HasScrollbar(VERTICAL))
      continue;

    float height = layer_impl->clip_height();

    // These magical values match WebKit and are designed to scroll nearly the
    // entire visible content height but leave a bit of overlap.
    float page = std::max(height * 0.875f, 1.f);
    if (direction == SCROLL_BACKWARD)
      page = -page;

    gfx::Vector2dF delta = gfx::Vector2dF(0.f, page);

    gfx::Vector2dF applied_delta = ScrollLayerWithLocalDelta(layer_impl, delta);

    if (!applied_delta.IsZero()) {
      client_->SetNeedsCommitOnImplThread();
      SetNeedsRedraw();
      client_->RenewTreePriority();
      return true;
    }

    active_tree_->SetCurrentlyScrollingLayer(layer_impl);
  }

  return false;
}

void LayerTreeHostImpl::SetRootLayerScrollOffsetDelegate(
      LayerScrollOffsetDelegate* root_layer_scroll_offset_delegate) {
  root_layer_scroll_offset_delegate_ = root_layer_scroll_offset_delegate;
  active_tree_->SetRootLayerScrollOffsetDelegate(
      root_layer_scroll_offset_delegate_);
}

void LayerTreeHostImpl::OnRootLayerDelegatedScrollOffsetChanged() {
  DCHECK(root_layer_scroll_offset_delegate_ != NULL);
  client_->SetNeedsCommitOnImplThread();
}

void LayerTreeHostImpl::ClearCurrentlyScrollingLayer() {
  active_tree_->ClearCurrentlyScrollingLayer();
  did_lock_scrolling_layer_ = false;
  scroll_affects_scroll_handler_ = false;
  accumulated_root_overscroll_ = gfx::Vector2dF();
}

void LayerTreeHostImpl::ScrollEnd() {
  if (top_controls_manager_)
    top_controls_manager_->ScrollEnd();
  ClearCurrentlyScrollingLayer();
  StartScrollbarAnimation();
}

InputHandler::ScrollStatus LayerTreeHostImpl::FlingScrollBegin() {
  if (!active_tree_->CurrentlyScrollingLayer())
    return ScrollIgnored;

  if (settings_.ignore_root_layer_flings &&
      (active_tree_->CurrentlyScrollingLayer() == InnerViewportScrollLayer() ||
       active_tree_->CurrentlyScrollingLayer() == OuterViewportScrollLayer())) {
    ClearCurrentlyScrollingLayer();
    return ScrollIgnored;
  }

  if (!wheel_scrolling_) {
    // Allow the fling to lock to the first layer that moves after the initial
    // fling |ScrollBy()| event.
    did_lock_scrolling_layer_ = false;
    should_bubble_scrolls_ = false;
  }

  return ScrollStarted;
}

float LayerTreeHostImpl::DeviceSpaceDistanceToLayer(
    const gfx::PointF& device_viewport_point,
    LayerImpl* layer_impl) {
  if (!layer_impl)
    return std::numeric_limits<float>::max();

  gfx::Rect layer_impl_bounds(
      layer_impl->content_bounds());

  gfx::RectF device_viewport_layer_impl_bounds = MathUtil::MapClippedRect(
      layer_impl->screen_space_transform(),
      layer_impl_bounds);

  return device_viewport_layer_impl_bounds.ManhattanDistanceToPoint(
      device_viewport_point);
}

void LayerTreeHostImpl::MouseMoveAt(const gfx::Point& viewport_point) {
  if (!EnsureRenderSurfaceLayerList())
    return;

  gfx::PointF device_viewport_point = gfx::ScalePoint(viewport_point,
                                                      device_scale_factor_);

  LayerImpl* layer_impl = LayerTreeHostCommon::FindLayerThatIsHitByPoint(
      device_viewport_point,
      active_tree_->RenderSurfaceLayerList());
  if (HandleMouseOverScrollbar(layer_impl, device_viewport_point))
    return;

  if (scroll_layer_id_when_mouse_over_scrollbar_) {
    LayerImpl* scroll_layer_impl = active_tree_->LayerById(
        scroll_layer_id_when_mouse_over_scrollbar_);

    // The check for a null scroll_layer_impl below was added to see if it will
    // eliminate the crashes described in http://crbug.com/326635.
    // TODO(wjmaclean) Add a unit test if this fixes the crashes.
    ScrollbarAnimationController* animation_controller =
        scroll_layer_impl ? scroll_layer_impl->scrollbar_animation_controller()
                          : NULL;
    if (animation_controller) {
      animation_controller->DidMouseMoveOffScrollbar(CurrentFrameTimeTicks());
      StartScrollbarAnimation();
    }
    scroll_layer_id_when_mouse_over_scrollbar_ = 0;
  }

  bool scroll_on_main_thread = false;
  LayerImpl* scroll_layer_impl =
      FindScrollLayerForDeviceViewportPoint(device_viewport_point,
                                            InputHandler::Gesture,
                                            layer_impl,
                                            &scroll_on_main_thread,
                                            NULL);
  if (scroll_on_main_thread || !scroll_layer_impl)
    return;

  ScrollbarAnimationController* animation_controller =
      scroll_layer_impl->scrollbar_animation_controller();
  if (!animation_controller)
    return;

  // TODO(wjmaclean) Is it ok to choose distance from more than two scrollbars?
  float distance_to_scrollbar = std::numeric_limits<float>::max();
  for (LayerImpl::ScrollbarSet::iterator it =
           scroll_layer_impl->scrollbars()->begin();
       it != scroll_layer_impl->scrollbars()->end();
       ++it)
    distance_to_scrollbar =
        std::min(distance_to_scrollbar,
                 DeviceSpaceDistanceToLayer(device_viewport_point, *it));

  bool should_animate = animation_controller->DidMouseMoveNear(
      CurrentFrameTimeTicks(), distance_to_scrollbar / device_scale_factor_);
  if (should_animate)
    StartScrollbarAnimation();
}

bool LayerTreeHostImpl::HandleMouseOverScrollbar(LayerImpl* layer_impl,
    const gfx::PointF& device_viewport_point) {
  if (layer_impl && layer_impl->ToScrollbarLayer()) {
    int scroll_layer_id = layer_impl->ToScrollbarLayer()->ScrollLayerId();
    layer_impl = active_tree_->LayerById(scroll_layer_id);
    if (layer_impl && layer_impl->scrollbar_animation_controller()) {
      scroll_layer_id_when_mouse_over_scrollbar_ = scroll_layer_id;
      bool should_animate =
          layer_impl->scrollbar_animation_controller()->DidMouseMoveNear(
              CurrentFrameTimeTicks(), 0);
      if (should_animate)
        StartScrollbarAnimation();
    } else {
      scroll_layer_id_when_mouse_over_scrollbar_ = 0;
    }

    return true;
  }

  return false;
}

void LayerTreeHostImpl::PinchGestureBegin() {
  pinch_gesture_active_ = true;
  previous_pinch_anchor_ = gfx::Point();
  client_->RenewTreePriority();
  pinch_gesture_end_should_clear_scrolling_layer_ = !CurrentlyScrollingLayer();
  if (active_tree_->OuterViewportScrollLayer()) {
    active_tree_->SetCurrentlyScrollingLayer(
        active_tree_->OuterViewportScrollLayer());
  } else {
    active_tree_->SetCurrentlyScrollingLayer(
        active_tree_->InnerViewportScrollLayer());
  }
  if (top_controls_manager_)
    top_controls_manager_->PinchBegin();
}

void LayerTreeHostImpl::PinchGestureUpdate(float magnify_delta,
                                           const gfx::Point& anchor) {
  if (!InnerViewportScrollLayer())
    return;

  TRACE_EVENT0("cc", "LayerTreeHostImpl::PinchGestureUpdate");

  // Keep the center-of-pinch anchor specified by (x, y) in a stable
  // position over the course of the magnify.
  float page_scale_delta = active_tree_->page_scale_delta();
  gfx::PointF previous_scale_anchor =
      gfx::ScalePoint(anchor, 1.f / page_scale_delta);
  active_tree_->SetPageScaleDelta(page_scale_delta * magnify_delta);
  page_scale_delta = active_tree_->page_scale_delta();
  gfx::PointF new_scale_anchor =
      gfx::ScalePoint(anchor, 1.f / page_scale_delta);
  gfx::Vector2dF move = previous_scale_anchor - new_scale_anchor;

  previous_pinch_anchor_ = anchor;

  move.Scale(1 / active_tree_->page_scale_factor());
  // If clamping the inner viewport scroll offset causes a change, it should
  // be accounted for from the intended move.
  move -= InnerViewportScrollLayer()->ClampScrollToMaxScrollOffset();

  // We manually manage the bubbling behaviour here as it is different to that
  // implemented in LayerTreeHostImpl::ScrollBy(). Specifically:
  // 1) we want to explicit limit the bubbling to the outer/inner viewports,
  // 2) we don't want the directional limitations on the unused parts that
  //    ScrollBy() implements, and
  // 3) pinching should not engage the top controls manager.
  gfx::Vector2dF unused = OuterViewportScrollLayer()
                              ? OuterViewportScrollLayer()->ScrollBy(move)
                              : move;

  if (!unused.IsZero()) {
    InnerViewportScrollLayer()->ScrollBy(unused);
    InnerViewportScrollLayer()->ClampScrollToMaxScrollOffset();
  }

  client_->SetNeedsCommitOnImplThread();
  SetNeedsRedraw();
  client_->RenewTreePriority();
}

void LayerTreeHostImpl::PinchGestureEnd() {
  pinch_gesture_active_ = false;
  if (pinch_gesture_end_should_clear_scrolling_layer_) {
    pinch_gesture_end_should_clear_scrolling_layer_ = false;
    ClearCurrentlyScrollingLayer();
  }
  if (top_controls_manager_)
    top_controls_manager_->PinchEnd();
  client_->SetNeedsCommitOnImplThread();
}

static void CollectScrollDeltas(ScrollAndScaleSet* scroll_info,
                                LayerImpl* layer_impl) {
  if (!layer_impl)
    return;

  gfx::Vector2d scroll_delta =
      gfx::ToFlooredVector2d(layer_impl->ScrollDelta());
  if (!scroll_delta.IsZero()) {
    LayerTreeHostCommon::ScrollUpdateInfo scroll;
    scroll.layer_id = layer_impl->id();
    scroll.scroll_delta = scroll_delta;
    scroll_info->scrolls.push_back(scroll);
    layer_impl->SetSentScrollDelta(scroll_delta);
  }

  for (size_t i = 0; i < layer_impl->children().size(); ++i)
    CollectScrollDeltas(scroll_info, layer_impl->children()[i]);
}

scoped_ptr<ScrollAndScaleSet> LayerTreeHostImpl::ProcessScrollDeltas() {
  scoped_ptr<ScrollAndScaleSet> scroll_info(new ScrollAndScaleSet());

  CollectScrollDeltas(scroll_info.get(), active_tree_->root_layer());
  scroll_info->page_scale_delta = active_tree_->page_scale_delta();
  active_tree_->set_sent_page_scale_delta(scroll_info->page_scale_delta);

  return scroll_info.Pass();
}

void LayerTreeHostImpl::SetFullRootLayerDamage() {
  SetViewportDamage(gfx::Rect(DrawViewportSize()));
}

void LayerTreeHostImpl::ScrollViewportBy(gfx::Vector2dF scroll_delta) {
  DCHECK(InnerViewportScrollLayer());
  LayerImpl* scroll_layer = OuterViewportScrollLayer()
                                ? OuterViewportScrollLayer()
                                : InnerViewportScrollLayer();

  gfx::Vector2dF unused_delta = scroll_layer->ScrollBy(scroll_delta);

  if (!unused_delta.IsZero() && (scroll_layer == OuterViewportScrollLayer()))
    InnerViewportScrollLayer()->ScrollBy(unused_delta);
}

void LayerTreeHostImpl::AnimatePageScale(base::TimeTicks monotonic_time) {
  if (!page_scale_animation_)
    return;

  // TODO(ajuma): http://crbug.com/178171 - Animations use double for monotonic
  // time.
  double monotonic_time_for_cc_animations =
      (monotonic_time - base::TimeTicks()).InSecondsF();
  gfx::Vector2dF scroll_total = active_tree_->TotalScrollOffset();

  if (!page_scale_animation_->IsAnimationStarted())
    page_scale_animation_->StartAnimation(monotonic_time_for_cc_animations);

  active_tree_->SetPageScaleDelta(page_scale_animation_->PageScaleFactorAtTime(
                                      monotonic_time_for_cc_animations) /
                                  active_tree_->page_scale_factor());
  gfx::Vector2dF next_scroll = page_scale_animation_->ScrollOffsetAtTime(
      monotonic_time_for_cc_animations);

  ScrollViewportBy(next_scroll - scroll_total);
  SetNeedsRedraw();

  if (page_scale_animation_->IsAnimationCompleteAtTime(
          monotonic_time_for_cc_animations)) {
    page_scale_animation_.reset();
    client_->SetNeedsCommitOnImplThread();
    client_->RenewTreePriority();
  }
}

void LayerTreeHostImpl::AnimateTopControls(base::TimeTicks time) {
  if (!top_controls_manager_ || !top_controls_manager_->animation())
    return;
  gfx::Vector2dF scroll = top_controls_manager_->Animate(time);
  if (active_tree_->TotalScrollOffset().y() == 0.f)
    return;
  if (scroll.IsZero()) {
    // This may happen on the first animation step. Force redraw otherwise
    // the animation would stop because of no new frames.
    SetNeedsRedraw();
  } else {
    ScrollViewportBy(gfx::ScaleVector2d(
        scroll, 1.f / active_tree_->total_page_scale_factor()));
  }
}

void LayerTreeHostImpl::AnimateLayers(base::TimeTicks monotonic_time) {
  if (!settings_.accelerated_animation_enabled ||
      !needs_animate_layers() ||
      !active_tree_->root_layer())
    return;

  TRACE_EVENT0("cc", "LayerTreeHostImpl::AnimateLayers");

  // TODO(ajuma): http://crbug.com/178171 - Animations use double for monotonic
  // time.
  double monotonic_time_for_cc_animations =
      (monotonic_time - base::TimeTicks()).InSecondsF();
  AnimationRegistrar::AnimationControllerMap copy =
      animation_registrar_->active_animation_controllers();
  for (AnimationRegistrar::AnimationControllerMap::iterator iter = copy.begin();
       iter != copy.end();
       ++iter)
    (*iter).second->Animate(monotonic_time_for_cc_animations);

  SetNeedsRedraw();
}

void LayerTreeHostImpl::UpdateAnimationState(bool start_ready_animations) {
  if (!settings_.accelerated_animation_enabled ||
      !needs_animate_layers() ||
      !active_tree_->root_layer())
    return;

  TRACE_EVENT0("cc", "LayerTreeHostImpl::UpdateAnimationState");
  scoped_ptr<AnimationEventsVector> events =
      make_scoped_ptr(new AnimationEventsVector);
  AnimationRegistrar::AnimationControllerMap copy =
      animation_registrar_->active_animation_controllers();
  for (AnimationRegistrar::AnimationControllerMap::iterator iter = copy.begin();
       iter != copy.end();
       ++iter)
    (*iter).second->UpdateState(start_ready_animations, events.get());

  if (!events->empty()) {
    client_->PostAnimationEventsToMainThreadOnImplThread(events.Pass());
  }
}

base::TimeDelta LayerTreeHostImpl::LowFrequencyAnimationInterval() const {
  return base::TimeDelta::FromSeconds(1);
}

void LayerTreeHostImpl::SendReleaseResourcesRecursive(LayerImpl* current) {
  DCHECK(current);
  current->ReleaseResources();
  if (current->mask_layer())
    SendReleaseResourcesRecursive(current->mask_layer());
  if (current->replica_layer())
    SendReleaseResourcesRecursive(current->replica_layer());
  for (size_t i = 0; i < current->children().size(); ++i)
    SendReleaseResourcesRecursive(current->children()[i]);
}

void LayerTreeHostImpl::SetOffscreenContextProvider(
    const scoped_refptr<ContextProvider>& offscreen_context_provider) {
  if (!offscreen_context_provider.get()) {
    offscreen_context_provider_ = NULL;
    return;
  }

  if (!offscreen_context_provider->BindToCurrentThread()) {
    offscreen_context_provider_ = NULL;
    return;
  }

  offscreen_context_provider_ = offscreen_context_provider;
}

std::string LayerTreeHostImpl::LayerTreeAsJson() const {
  std::string str;
  if (active_tree_->root_layer()) {
    scoped_ptr<base::Value> json(active_tree_->root_layer()->LayerTreeAsJson());
    base::JSONWriter::WriteWithOptions(
        json.get(), base::JSONWriter::OPTIONS_PRETTY_PRINT, &str);
  }
  return str;
}

int LayerTreeHostImpl::SourceAnimationFrameNumber() const {
  return fps_counter_->current_frame_number();
}

void LayerTreeHostImpl::SendManagedMemoryStats(
    size_t memory_visible_bytes,
    size_t memory_visible_and_nearby_bytes,
    size_t memory_use_bytes) {
  if (!renderer_)
    return;

  // Round the numbers being sent up to the next 8MB, to throttle the rate
  // at which we spam the GPU process.
  static const size_t rounding_step = 8 * 1024 * 1024;
  memory_visible_bytes = RoundUp(memory_visible_bytes, rounding_step);
  memory_visible_and_nearby_bytes = RoundUp(memory_visible_and_nearby_bytes,
                                            rounding_step);
  memory_use_bytes = RoundUp(memory_use_bytes, rounding_step);
  if (last_sent_memory_visible_bytes_ == memory_visible_bytes &&
      last_sent_memory_visible_and_nearby_bytes_ ==
          memory_visible_and_nearby_bytes &&
      last_sent_memory_use_bytes_ == memory_use_bytes) {
    return;
  }
  last_sent_memory_visible_bytes_ = memory_visible_bytes;
  last_sent_memory_visible_and_nearby_bytes_ = memory_visible_and_nearby_bytes;
  last_sent_memory_use_bytes_ = memory_use_bytes;

  renderer_->SendManagedMemoryStats(last_sent_memory_visible_bytes_,
                                    last_sent_memory_visible_and_nearby_bytes_,
                                    last_sent_memory_use_bytes_);
}

void LayerTreeHostImpl::AnimateScrollbars(base::TimeTicks time) {
  AnimateScrollbarsRecursive(active_tree_->root_layer(), time);
}

void LayerTreeHostImpl::AnimateScrollbarsRecursive(LayerImpl* layer,
                                                   base::TimeTicks time) {
  if (!layer)
    return;

  ScrollbarAnimationController* scrollbar_controller =
      layer->scrollbar_animation_controller();
  if (scrollbar_controller && scrollbar_controller->Animate(time)) {
    TRACE_EVENT_INSTANT0(
        "cc", "LayerTreeHostImpl::SetNeedsRedraw due to AnimateScrollbars",
        TRACE_EVENT_SCOPE_THREAD);
    SetNeedsRedraw();
  }

  for (size_t i = 0; i < layer->children().size(); ++i)
    AnimateScrollbarsRecursive(layer->children()[i], time);
}

void LayerTreeHostImpl::StartScrollbarAnimation() {
  TRACE_EVENT0("cc", "LayerTreeHostImpl::StartScrollbarAnimation");
  StartScrollbarAnimationRecursive(RootLayer(), CurrentFrameTimeTicks());
}

void LayerTreeHostImpl::StartScrollbarAnimationRecursive(LayerImpl* layer,
                                                         base::TimeTicks time) {
  if (!layer)
    return;

  ScrollbarAnimationController* scrollbar_controller =
      layer->scrollbar_animation_controller();
  if (scrollbar_controller && scrollbar_controller->IsAnimating()) {
    base::TimeDelta delay = scrollbar_controller->DelayBeforeStart(time);
    if (delay > base::TimeDelta())
      client_->RequestScrollbarAnimationOnImplThread(delay);
    else if (scrollbar_controller->Animate(time))
      SetNeedsRedraw();
  }

  for (size_t i = 0; i < layer->children().size(); ++i)
    StartScrollbarAnimationRecursive(layer->children()[i], time);
}

void LayerTreeHostImpl::SetTreePriority(TreePriority priority) {
  if (!tile_manager_)
    return;

  if (global_tile_state_.tree_priority == priority)
    return;
  global_tile_state_.tree_priority = priority;
  DidModifyTilePriorities();
}

void LayerTreeHostImpl::UpdateCurrentFrameTime() {
  DCHECK(current_frame_timeticks_.is_null());
  current_frame_timeticks_ = gfx::FrameTime::Now();
}

void LayerTreeHostImpl::ResetCurrentFrameTimeForNextFrame() {
  current_frame_timeticks_ = base::TimeTicks();
}

base::TimeTicks LayerTreeHostImpl::CurrentFrameTimeTicks() {
  // Try to use the current frame time to keep animations non-jittery.  But if
  // we're not in a frame (because this is during an input event or a delayed
  // task), fall back to physical time.  This should still be monotonic.
  if (!current_frame_timeticks_.is_null())
    return current_frame_timeticks_;
  return gfx::FrameTime::Now();
}

scoped_ptr<base::Value> LayerTreeHostImpl::AsValueWithFrame(
    FrameData* frame) const {
  scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
  if (this->pending_tree_)
      state->Set("activation_state", ActivationStateAsValue().release());
  state->Set("device_viewport_size",
             MathUtil::AsValue(device_viewport_size_).release());
  if (tile_manager_)
    state->Set("tiles", tile_manager_->AllTilesAsValue().release());
  state->Set("active_tree", active_tree_->AsValue().release());
  if (pending_tree_)
    state->Set("pending_tree", pending_tree_->AsValue().release());
  if (frame)
    state->Set("frame", frame->AsValue().release());
  return state.PassAs<base::Value>();
}

scoped_ptr<base::Value> LayerTreeHostImpl::ActivationStateAsValue() const {
  scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
  state->Set("lthi", TracedValue::CreateIDRef(this).release());
  if (tile_manager_)
    state->Set("tile_manager", tile_manager_->BasicStateAsValue().release());
  return state.PassAs<base::Value>();
}

void LayerTreeHostImpl::SetDebugState(
    const LayerTreeDebugState& new_debug_state) {
  if (LayerTreeDebugState::Equal(debug_state_, new_debug_state))
    return;
  if (debug_state_.continuous_painting != new_debug_state.continuous_painting)
    paint_time_counter_->ClearHistory();

  debug_state_ = new_debug_state;
  UpdateTileManagerMemoryPolicy(ActualManagedMemoryPolicy());
  SetFullRootLayerDamage();
}

void LayerTreeHostImpl::CreateUIResource(UIResourceId uid,
                                         const UIResourceBitmap& bitmap) {
  DCHECK_GT(uid, 0);

  GLint wrap_mode = 0;
  switch (bitmap.GetWrapMode()) {
    case UIResourceBitmap::CLAMP_TO_EDGE:
      wrap_mode = GL_CLAMP_TO_EDGE;
      break;
    case UIResourceBitmap::REPEAT:
      wrap_mode = GL_REPEAT;
      break;
  }

  // Allow for multiple creation requests with the same UIResourceId.  The
  // previous resource is simply deleted.
  ResourceProvider::ResourceId id = ResourceIdForUIResource(uid);
  if (id)
    DeleteUIResource(uid);

  ResourceFormat format = resource_provider_->best_texture_format();
  if (bitmap.GetFormat() == UIResourceBitmap::ETC1)
    format = ETC1;
  id = resource_provider_->CreateResource(
      bitmap.GetSize(),
      wrap_mode,
      ResourceProvider::TextureUsageAny,
      format);

  UIResourceData data;
  data.resource_id = id;
  data.size = bitmap.GetSize();
  data.opaque = bitmap.GetOpaque();

  ui_resource_map_[uid] = data;

  AutoLockUIResourceBitmap bitmap_lock(bitmap);
  resource_provider_->SetPixels(id,
                                bitmap_lock.GetPixels(),
                                gfx::Rect(bitmap.GetSize()),
                                gfx::Rect(bitmap.GetSize()),
                                gfx::Vector2d(0, 0));
  MarkUIResourceNotEvicted(uid);
}

void LayerTreeHostImpl::DeleteUIResource(UIResourceId uid) {
  ResourceProvider::ResourceId id = ResourceIdForUIResource(uid);
  if (id) {
    resource_provider_->DeleteResource(id);
    ui_resource_map_.erase(uid);
  }
  MarkUIResourceNotEvicted(uid);
}

void LayerTreeHostImpl::EvictAllUIResources() {
  if (ui_resource_map_.empty())
    return;

  for (UIResourceMap::const_iterator iter = ui_resource_map_.begin();
      iter != ui_resource_map_.end();
      ++iter) {
    evicted_ui_resources_.insert(iter->first);
    resource_provider_->DeleteResource(iter->second.resource_id);
  }
  ui_resource_map_.clear();

  client_->SetNeedsCommitOnImplThread();
  client_->OnCanDrawStateChanged(CanDraw());
  client_->RenewTreePriority();
}

ResourceProvider::ResourceId LayerTreeHostImpl::ResourceIdForUIResource(
    UIResourceId uid) const {
  UIResourceMap::const_iterator iter = ui_resource_map_.find(uid);
  if (iter != ui_resource_map_.end())
    return iter->second.resource_id;
  return 0;
}

bool LayerTreeHostImpl::IsUIResourceOpaque(UIResourceId uid) const {
  UIResourceMap::const_iterator iter = ui_resource_map_.find(uid);
  DCHECK(iter != ui_resource_map_.end());
  return iter->second.opaque;
}

bool LayerTreeHostImpl::EvictedUIResourcesExist() const {
  return !evicted_ui_resources_.empty();
}

void LayerTreeHostImpl::MarkUIResourceNotEvicted(UIResourceId uid) {
  std::set<UIResourceId>::iterator found_in_evicted =
      evicted_ui_resources_.find(uid);
  if (found_in_evicted == evicted_ui_resources_.end())
    return;
  evicted_ui_resources_.erase(found_in_evicted);
  if (evicted_ui_resources_.empty())
    client_->OnCanDrawStateChanged(CanDraw());
}

void LayerTreeHostImpl::ScheduleMicroBenchmark(
    scoped_ptr<MicroBenchmarkImpl> benchmark) {
  micro_benchmark_controller_.ScheduleRun(benchmark.Pass());
}

void LayerTreeHostImpl::InsertSwapPromiseMonitor(SwapPromiseMonitor* monitor) {
  swap_promise_monitor_.insert(monitor);
}

void LayerTreeHostImpl::RemoveSwapPromiseMonitor(SwapPromiseMonitor* monitor) {
  swap_promise_monitor_.erase(monitor);
}

void LayerTreeHostImpl::NotifySwapPromiseMonitorsOfSetNeedsRedraw() {
  std::set<SwapPromiseMonitor*>::iterator it = swap_promise_monitor_.begin();
  for (; it != swap_promise_monitor_.end(); it++)
    (*it)->OnSetNeedsRedrawOnImpl();
}

}  // namespace cc