cc/trees/layer_tree_host_impl.h

// 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.

#ifndef CC_TREES_LAYER_TREE_HOST_IMPL_H_
#define CC_TREES_LAYER_TREE_HOST_IMPL_H_

#include <stddef.h>

#include <memory>
#include <set>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>

#include "base/callback.h"
#include "base/containers/flat_map.h"
#include "base/containers/flat_set.h"
#include "base/containers/mru_cache.h"
#include "base/memory/memory_pressure_listener.h"
#include "base/memory/shared_memory_mapping.h"
#include "base/sequenced_task_runner.h"
#include "base/time/time.h"
#include "cc/base/synced_property.h"
#include "cc/benchmarks/micro_benchmark_controller_impl.h"
#include "cc/cc_export.h"
#include "cc/input/actively_scrolling_type.h"
#include "cc/input/browser_controls_offset_manager_client.h"
#include "cc/input/input_handler.h"
#include "cc/input/scrollbar_animation_controller.h"
#include "cc/input/scrollbar_controller.h"
#include "cc/input/threaded_input_handler.h"
#include "cc/layers/layer_collections.h"
#include "cc/metrics/average_lag_tracking_manager.h"
#include "cc/metrics/dropped_frame_counter.h"
#include "cc/metrics/event_metrics.h"
#include "cc/metrics/events_metrics_manager.h"
#include "cc/metrics/frame_sequence_tracker_collection.h"
#include "cc/metrics/total_frame_counter.h"
#include "cc/paint/discardable_image_map.h"
#include "cc/paint/paint_worklet_job.h"
#include "cc/raster/raster_query_queue.h"
#include "cc/resources/ui_resource_client.h"
#include "cc/scheduler/begin_frame_tracker.h"
#include "cc/scheduler/commit_earlyout_reason.h"
#include "cc/scheduler/draw_result.h"
#include "cc/scheduler/scheduler.h"
#include "cc/scheduler/video_frame_controller.h"
#include "cc/tiles/decoded_image_tracker.h"
#include "cc/tiles/image_decode_cache.h"
#include "cc/tiles/tile_manager.h"
#include "cc/trees/animated_paint_worklet_tracker.h"
#include "cc/trees/de_jelly_state.h"
#include "cc/trees/frame_rate_estimator.h"
#include "cc/trees/layer_tree_frame_sink_client.h"
#include "cc/trees/layer_tree_host.h"
#include "cc/trees/layer_tree_mutator.h"
#include "cc/trees/layer_tree_settings.h"
#include "cc/trees/managed_memory_policy.h"
#include "cc/trees/mutator_host_client.h"
#include "cc/trees/presentation_time_callback_buffer.h"
#include "cc/trees/render_frame_metadata.h"
#include "cc/trees/task_runner_provider.h"
#include "cc/trees/throttle_decider.h"
#include "cc/trees/ukm_manager.h"
#include "components/viz/client/client_resource_provider.h"
#include "components/viz/common/frame_sinks/begin_frame_args.h"
#include "components/viz/common/gpu/context_cache_controller.h"
#include "components/viz/common/quads/compositor_render_pass.h"
#include "components/viz/common/surfaces/child_local_surface_id_allocator.h"
#include "components/viz/common/surfaces/local_surface_id.h"
#include "components/viz/common/surfaces/surface_id.h"
#include "components/viz/common/surfaces/surface_range.h"
#include "third_party/abseil-cpp/absl/types/optional.h"
#include "ui/events/types/scroll_input_type.h"
#include "ui/gfx/geometry/rect.h"

namespace gfx {
class ScrollOffset;
}

namespace viz {
class CompositorFrame;
class CompositorFrameMetadata;
struct FrameTimingDetails;
}  // namespace viz

namespace cc {

enum class ActivelyScrollingType;
class BrowserControlsOffsetManager;
class CompositorFrameReportingController;
class RasterDarkModeFilter;
class DebugRectHistory;
class EvictionTilePriorityQueue;
class DroppedFrameCounter;
class ImageAnimationController;
class LCDTextMetricsReporter;
class LayerImpl;
class LayerTreeFrameSink;
class LayerTreeImpl;
class PaintWorkletLayerPainter;
class MemoryHistory;
class MutatorEvents;
class MutatorHost;
class PageScaleAnimation;
class PendingTreeRasterDurationHistogramTimer;
class RasterTilePriorityQueue;
class RasterBufferProvider;
class RenderFrameMetadataObserver;
class RenderingStatsInstrumentation;
class ResourcePool;
class SwapPromise;
class SwapPromiseMonitor;
class SynchronousTaskGraphRunner;
class TaskGraphRunner;
class UIResourceBitmap;
class Viewport;

enum class GpuRasterizationStatus {
  ON,
  OFF_FORCED,
  OFF_DEVICE,
};

// LayerTreeHost->Proxy callback interface.
class LayerTreeHostImplClient {
 public:
  virtual void DidLoseLayerTreeFrameSinkOnImplThread() = 0;
  virtual void SetBeginFrameSource(viz::BeginFrameSource* source) = 0;
  virtual void DidReceiveCompositorFrameAckOnImplThread() = 0;
  virtual void OnCanDrawStateChanged(bool can_draw) = 0;
  virtual void NotifyReadyToActivate() = 0;
  virtual void NotifyReadyToDraw() = 0;
  // Please call these 2 functions through
  // LayerTreeHostImpl's SetNeedsRedraw() and SetNeedsOneBeginImplFrame().
  virtual void SetNeedsRedrawOnImplThread() = 0;
  virtual void SetNeedsOneBeginImplFrameOnImplThread() = 0;
  virtual void SetNeedsCommitOnImplThread() = 0;
  virtual void SetNeedsPrepareTilesOnImplThread() = 0;
  virtual void SetVideoNeedsBeginFrames(bool needs_begin_frames) = 0;
  virtual bool IsInsideDraw() = 0;
  virtual void RenewTreePriority() = 0;
  virtual void PostDelayedAnimationTaskOnImplThread(base::OnceClosure task,
                                                    base::TimeDelta delay) = 0;
  virtual void DidActivateSyncTree() = 0;
  virtual void WillPrepareTiles() = 0;
  virtual void DidPrepareTiles() = 0;

  // Called when page scale animation has completed on the impl thread.
  virtual void DidCompletePageScaleAnimationOnImplThread() = 0;

  // Called when output surface asks for a draw.
  virtual void OnDrawForLayerTreeFrameSink(bool resourceless_software_draw,
                                           bool skip_draw) = 0;

  virtual void NeedsImplSideInvalidation(
      bool needs_first_draw_on_activation) = 0;
  // Called when a requested image decode completes.
  virtual void NotifyImageDecodeRequestFinished() = 0;

  virtual void RequestBeginMainFrameNotExpected(bool new_state) = 0;

  // Called when a presentation time is requested. |frame_token| identifies
  // the frame that was presented. |callbacks| holds both impl side and main
  // side callbacks to be called.
  virtual void DidPresentCompositorFrameOnImplThread(
      uint32_t frame_token,
      PresentationTimeCallbackBuffer::PendingCallbacks callbacks,
      const viz::FrameTimingDetails& details) = 0;

  // Returns whether the main-thread is expected to receive a BeginMainFrame.
  virtual bool IsBeginMainFrameExpected() = 0;

  virtual void NotifyAnimationWorkletStateChange(
      AnimationWorkletMutationState state,
      ElementListType tree_type) = 0;

  virtual void NotifyPaintWorkletStateChange(
      Scheduler::PaintWorkletState state) = 0;

  virtual void NotifyThroughputTrackerResults(CustomTrackerResults results) = 0;

  virtual void DidObserveFirstScrollDelay(
      base::TimeDelta first_scroll_delay,
      base::TimeTicks first_scroll_timestamp) = 0;

  // Returns true if the client is currently compositing synchronously. This is
  // only true in tests, but some behavior needs to be synchronized in non-test
  // code as a result.
  virtual bool IsInSynchronousComposite() const = 0;

  virtual void FrameSinksToThrottleUpdated(
      const base::flat_set<viz::FrameSinkId>& ids) = 0;

 protected:
  virtual ~LayerTreeHostImplClient() = default;
};

// LayerTreeHostImpl owns the LayerImpl trees as well as associated rendering
// state.
class CC_EXPORT LayerTreeHostImpl : public TileManagerClient,
                                    public LayerTreeFrameSinkClient,
                                    public BrowserControlsOffsetManagerClient,
                                    public ScrollbarAnimationControllerClient,
                                    public VideoFrameControllerClient,
                                    public MutatorHostClient,
                                    public ImageAnimationController::Client,
                                    public CompositorDelegateForInput {
 public:
  // This structure is used to build all the state required for producing a
  // single CompositorFrame. The |render_passes| list becomes the set of
  // RenderPasses in the quad, and the other fields are used for computation
  // or become part of the CompositorFrameMetadata.
  struct CC_EXPORT FrameData {
    FrameData();
    FrameData(const FrameData&) = delete;
    ~FrameData();

    FrameData& operator=(const FrameData&) = delete;
    void AsValueInto(base::trace_event::TracedValue* value) const;
    std::string ToString() const;

    // frame_token is populated by the LayerTreeHostImpl when submitted.
    uint32_t frame_token = 0;

    bool has_missing_content = false;

    std::vector<viz::SurfaceId> activation_dependencies;
    absl::optional<uint32_t> deadline_in_frames;
    bool use_default_lower_bound_deadline = false;
    viz::CompositorRenderPassList render_passes;
    const RenderSurfaceList* render_surface_list = nullptr;
    LayerImplList will_draw_layers;
    bool has_no_damage = false;
    bool may_contain_video = false;
    viz::BeginFrameAck begin_frame_ack;
    // The original BeginFrameArgs that triggered the latest update from the
    // main thread.
    viz::BeginFrameArgs origin_begin_main_frame_args;
  };

  // A struct of data for a single UIResource, including the backing
  // pixels, and metadata about it.
  struct CC_EXPORT UIResourceData {
    UIResourceData();
    UIResourceData(const UIResourceData&) = delete;
    UIResourceData(UIResourceData&&) noexcept;
    ~UIResourceData();

    UIResourceData& operator=(const UIResourceData&) = delete;
    UIResourceData& operator=(UIResourceData&&);

    bool opaque;
    viz::ResourceFormat format;

    // Backing for software compositing.
    viz::SharedBitmapId shared_bitmap_id;
    base::WritableSharedMemoryMapping shared_mapping;
    // Backing for gpu compositing.
    gpu::Mailbox mailbox;

    // The name with which to refer to the resource in frames submitted to the
    // display compositor.
    viz::ResourceId resource_id_for_export;
  };

  static std::unique_ptr<LayerTreeHostImpl> Create(
      const LayerTreeSettings& settings,
      LayerTreeHostImplClient* client,
      TaskRunnerProvider* task_runner_provider,
      RenderingStatsInstrumentation* rendering_stats_instrumentation,
      TaskGraphRunner* task_graph_runner,
      std::unique_ptr<MutatorHost> mutator_host,
      RasterDarkModeFilter* dark_mode_filter,
      int id,
      scoped_refptr<base::SequencedTaskRunner> image_worker_task_runner,
      LayerTreeHostSchedulingClient* scheduling_client);
  LayerTreeHostImpl(const LayerTreeHostImpl&) = delete;
  ~LayerTreeHostImpl() override;

  LayerTreeHostImpl& operator=(const LayerTreeHostImpl&) = delete;

  // TODO(bokan): This getter is an escape-hatch for code that hasn't yet been
  // cleaned up to decouple input from graphics. Callers should be cleaned up
  // to avoid calling it and it should be removed.
  ThreadedInputHandler& GetInputHandler();
  const ThreadedInputHandler& GetInputHandler() const;

  void StartPageScaleAnimation(const gfx::Vector2d& target_offset,
                               bool anchor_point,
                               float page_scale,
                               base::TimeDelta duration);
  void SetNeedsAnimateInput();
  std::unique_ptr<SwapPromiseMonitor> CreateLatencyInfoSwapPromiseMonitor(
      ui::LatencyInfo* latency);
  std::unique_ptr<EventsMetricsManager::ScopedMonitor>
  GetScopedEventMetricsMonitor(
      EventsMetricsManager::ScopedMonitor::DoneCallback done_callback);
  void NotifyInputEvent();

  // BrowserControlsOffsetManagerClient implementation.
  float TopControlsHeight() const override;
  float TopControlsMinHeight() const override;
  float BottomControlsHeight() const override;
  float BottomControlsMinHeight() const override;
  void SetCurrentBrowserControlsShownRatio(float top_ratio,
                                           float bottom_ratio) override;
  float CurrentTopControlsShownRatio() const override;
  float CurrentBottomControlsShownRatio() const override;
  gfx::ScrollOffset ViewportScrollOffset() const override;
  void DidChangeBrowserControlsPosition() override;
  void DidObserveScrollDelay(base::TimeDelta scroll_delay,
                             base::TimeTicks scroll_timestamp);
  bool OnlyExpandTopControlsAtPageTop() const override;
  bool HaveRootScrollNode() const override;
  void SetNeedsCommit() override;

  // ImageAnimationController::Client implementation.
  void RequestBeginFrameForAnimatedImages() override;
  void RequestInvalidationForAnimatedImages() override;

  EventMetricsSet TakeEventsMetrics();
  void AppendEventsMetricsFromMainThread(
      std::vector<EventMetrics> events_metrics);

  base::WeakPtr<LayerTreeHostImpl> AsWeakPtr();

  void set_resourceless_software_draw_for_testing() {
    resourceless_software_draw_ = true;
  }

  const gfx::Rect& viewport_damage_rect_for_testing() const {
    return viewport_damage_rect_;
  }

  virtual void WillSendBeginMainFrame();
  virtual void DidSendBeginMainFrame(const viz::BeginFrameArgs& args);
  virtual void BeginMainFrameAborted(
      CommitEarlyOutReason reason,
      std::vector<std::unique_ptr<SwapPromise>> swap_promises,
      const viz::BeginFrameArgs& args);
  virtual void ReadyToCommit(
      const viz::BeginFrameArgs& commit_args,
      const BeginMainFrameMetrics* begin_main_frame_metrics);
  virtual void BeginCommit();
  virtual void CommitComplete();
  virtual void UpdateAnimationState(bool start_ready_animations);
  bool Mutate(base::TimeTicks monotonic_time);
  void ActivateAnimations();
  void Animate();
  void AnimatePendingTreeAfterCommit();
  void DidAnimateScrollOffset();
  void SetFullViewportDamage();
  void SetViewportDamage(const gfx::Rect& damage_rect);
  void SetEnableFrameRateThrottling(bool enable_frame_rate_throttling);

  // Interface for ThreadedInputHandler
  void BindToInputHandler(
      std::unique_ptr<InputDelegateForCompositor> delegate) override;
  ScrollTree& GetScrollTree() const override;
  bool HasAnimatedScrollbars() const override;
  // Already overridden for BrowserControlsOffsetManagerClient which declares a
  // method of the same name.
  // void SetNeedsCommit();
  void SetNeedsFullViewportRedraw() override;
  void DidUpdateScrollAnimationCurve() override;
  void AccumulateScrollDeltaForTracing(const gfx::Vector2dF& delta) override;
  void DidStartPinchZoom() override;
  void DidUpdatePinchZoom() override;
  void DidEndPinchZoom() override;
  void DidStartScroll() override;
  void DidEndScroll() override;
  void DidMouseLeave() override;
  bool IsInHighLatencyMode() const override;
  void WillScrollContent(ElementId element_id) override;
  void DidScrollContent(ElementId element_id, bool animated) override;
  float DeviceScaleFactor() const override;
  float PageScaleFactor() const override;
  gfx::Size VisualDeviceViewportSize() const override;
  const LayerTreeSettings& GetSettings() const override;
  LayerTreeHostImpl& GetImplDeprecated() override;
  const LayerTreeHostImpl& GetImplDeprecated() const override;

  bool CanInjectJankOnMain() const;
  FrameSequenceTrackerCollection& frame_trackers() { return frame_trackers_; }

  // VisualDeviceViewportSize is the size of the global viewport across all
  // compositors that are part of the scene that this compositor contributes to
  // (i.e. the visual viewport), allowing for that scene to be broken up into
  // multiple compositors that each contribute to the whole (e.g. cross-origin
  // iframes are isolated from each other). This is a size instead of a rect
  // because each compositor doesn't know its position relative to other
  // compositors. This is specified in device viewport coordinate space.
  void SetVisualDeviceViewportSize(const gfx::Size&);

  void set_viewport_mobile_optimized(bool viewport_mobile_optimized) {
    is_viewport_mobile_optimized_ = viewport_mobile_optimized;
  }

  bool viewport_mobile_optimized() const {
    return is_viewport_mobile_optimized_;
  }

  // Updates registered ElementIds present in |changed_list|. Call this after
  // changing the property trees for the |changed_list| trees.
  void UpdateElements(ElementListType changed_list);

  // Analogous to a commit, this function is used to create a sync tree and
  // add impl-side invalidations to it.
  // virtual for testing.
  virtual void InvalidateContentOnImplSide();
  virtual void InvalidateLayerTreeFrameSink(bool needs_redraw);

  void SetTreeLayerScrollOffsetMutated(ElementId element_id,
                                       LayerTreeImpl* tree,
                                       const gfx::ScrollOffset& scroll_offset);
  void SetNeedUpdateGpuRasterizationStatus();
  bool NeedUpdateGpuRasterizationStatusForTesting() const {
    return need_update_gpu_rasterization_status_;
  }

  // MutatorHostClient implementation.
  bool IsElementInPropertyTrees(ElementId element_id,
                                ElementListType list_type) const override;
  void SetMutatorsNeedCommit() override;
  void SetMutatorsNeedRebuildPropertyTrees() override;
  void SetElementFilterMutated(ElementId element_id,
                               ElementListType list_type,
                               const FilterOperations& filters) override;
  void SetElementBackdropFilterMutated(
      ElementId element_id,
      ElementListType list_type,
      const FilterOperations& backdrop_filters) override;
  void SetElementOpacityMutated(ElementId element_id,
                                ElementListType list_type,
                                float opacity) override;
  void SetElementTransformMutated(ElementId element_id,
                                  ElementListType list_type,
                                  const gfx::Transform& transform) override;
  void SetElementScrollOffsetMutated(
      ElementId element_id,
      ElementListType list_type,
      const gfx::ScrollOffset& scroll_offset) override;
  void ElementIsAnimatingChanged(const PropertyToElementIdMap& element_id_map,
                                 ElementListType list_type,
                                 const PropertyAnimationState& mask,
                                 const PropertyAnimationState& state) override;
  void MaximumScaleChanged(ElementId element_id,
                           ElementListType list_type,
                           float maximum_scale) override;
  void OnCustomPropertyMutated(
      PaintWorkletInput::PropertyKey property_key,
      PaintWorkletInput::PropertyValue property_value) override;

  void ScrollOffsetAnimationFinished() override;
  gfx::ScrollOffset GetScrollOffsetForAnimation(
      ElementId element_id) const override;

  void NotifyAnimationWorkletStateChange(AnimationWorkletMutationState state,
                                         ElementListType tree_type) override;

  virtual bool PrepareTiles();

  // Returns DRAW_SUCCESS unless problems occured preparing the frame, and we
  // should try to avoid displaying the frame. If PrepareToDraw is called,
  // DidDrawAllLayers must also be called, regardless of whether DrawLayers is
  // called between the two.
  virtual DrawResult PrepareToDraw(FrameData* frame);
  virtual bool DrawLayers(FrameData* frame);
  viz::CompositorFrame GenerateCompositorFrame(FrameData* frame);
  // Must be called if and only if PrepareToDraw was called.
  void DidDrawAllLayers(const FrameData& frame);

  const LayerTreeSettings& settings() const { return settings_; }

  // Evict all textures by enforcing a memory policy with an allocation of 0.
  void EvictTexturesForTesting();

  // When blocking, this prevents client_->NotifyReadyToActivate() from being
  // called. When disabled, it calls client_->NotifyReadyToActivate()
  // immediately if any notifications had been blocked while blocking.
  virtual void BlockNotifyReadyToActivateForTesting(bool block);

  // Prevents notifying the |client_| when an impl side invalidation request is
  // made. When unblocked, the disabled request will immediately be called.
  virtual void BlockImplSideInvalidationRequestsForTesting(bool block);

  // Resets all of the trees to an empty state.
  void ResetTreesForTesting();

  size_t SourceAnimationFrameNumberForTesting() const;

  void RegisterScrollbarAnimationController(ElementId scroll_element_id,
                                            float initial_opacity);
  void DidUnregisterScrollbarLayer(ElementId scroll_element_id,
                                   ScrollbarOrientation orientation);
  ScrollbarAnimationController* ScrollbarAnimationControllerForElementId(
      ElementId scroll_element_id) const;
  void FlashAllScrollbars(bool did_scroll);

  DrawMode GetDrawMode() const;

  void DidNotNeedBeginFrame();

  // TileManagerClient implementation.
  void NotifyReadyToActivate() override;
  void NotifyReadyToDraw() override;
  void NotifyAllTileTasksCompleted() override;
  void NotifyTileStateChanged(const Tile* tile) override;
  std::unique_ptr<RasterTilePriorityQueue> BuildRasterQueue(
      TreePriority tree_priority,
      RasterTilePriorityQueue::Type type) override;
  std::unique_ptr<EvictionTilePriorityQueue> BuildEvictionQueue(
      TreePriority tree_priority) override;
  void SetIsLikelyToRequireADraw(bool is_likely_to_require_a_draw) override;
  gfx::ColorSpace GetRasterColorSpace(
      gfx::ContentColorUsage content_color_usage) const override;
  float GetSDRWhiteLevel() const override;
  void RequestImplSideInvalidationForCheckerImagedTiles() override;
  size_t GetFrameIndexForImage(const PaintImage& paint_image,
                               WhichTree tree) const override;
  int GetMSAASampleCountForRaster(
      const scoped_refptr<DisplayItemList>& display_list) override;

  bool HasPendingTree() override;

  // ScrollbarAnimationControllerClient implementation.
  void PostDelayedScrollbarAnimationTask(base::OnceClosure task,
                                         base::TimeDelta delay) override;
  void SetNeedsAnimateForScrollbarAnimation() override;
  void SetNeedsRedrawForScrollbarAnimation() override;
  ScrollbarSet ScrollbarsFor(ElementId scroll_element_id) const override;
  void DidChangeScrollbarVisibility() override;

  // VideoBeginFrameSource implementation.
  void AddVideoFrameController(VideoFrameController* controller) override;
  void RemoveVideoFrameController(VideoFrameController* controller) override;

  // LayerTreeFrameSinkClient implementation.
  void SetBeginFrameSource(viz::BeginFrameSource* source) override;
  void SetExternalTilePriorityConstraints(
      const gfx::Rect& viewport_rect,
      const gfx::Transform& transform) override;
  absl::optional<viz::HitTestRegionList> BuildHitTestData() override;
  void DidLoseLayerTreeFrameSink() override;
  void DidReceiveCompositorFrameAck() override;
  void DidPresentCompositorFrame(
      uint32_t frame_token,
      const viz::FrameTimingDetails& details) override;
  void ReclaimResources(std::vector<viz::ReturnedResource> resources) override;
  void SetMemoryPolicy(const ManagedMemoryPolicy& policy) override;
  void SetTreeActivationCallback(base::RepeatingClosure callback) override;
  void OnDraw(const gfx::Transform& transform,
              const gfx::Rect& viewport,
              bool resourceless_software_draw,
              bool skip_draw) override;
  void OnCompositorFrameTransitionDirectiveProcessed(
      uint32_t sequence_id) override;

  // Called from LayerTreeImpl.
  void OnCanDrawStateChangedForTree();

  // Implementation.
  int id() const { return id_; }
  bool CanDraw() const;
  LayerTreeFrameSink* layer_tree_frame_sink() const {
    return layer_tree_frame_sink_;
  }
  int max_texture_size() const { return max_texture_size_; }
  void ReleaseLayerTreeFrameSink();

  int RequestedMSAASampleCount() const;

  virtual bool InitializeFrameSink(LayerTreeFrameSink* layer_tree_frame_sink);
  TileManager* tile_manager() { return &tile_manager_; }

  void GetGpuRasterizationCapabilities(bool* gpu_rasterization_enabled,
                                       bool* gpu_rasterization_supported,
                                       int* max_msaa_samples,
                                       bool* supports_disable_msaa);
  bool use_gpu_rasterization() const { return use_gpu_rasterization_; }
  bool can_use_oop_rasterization() const { return can_use_oop_rasterization_; }
  bool use_oop_rasterization() const {
    return use_gpu_rasterization_ && can_use_oop_rasterization_;
  }

  GpuRasterizationStatus gpu_rasterization_status() const {
    return gpu_rasterization_status_;
  }

  bool create_low_res_tiling() const {
    return settings_.create_low_res_tiling && !use_gpu_rasterization_;
  }
  ResourcePool* resource_pool() { return resource_pool_.get(); }
  ImageDecodeCache* image_decode_cache() { return image_decode_cache_.get(); }
  ImageAnimationController* image_animation_controller() {
    return &image_animation_controller_;
  }

  uint32_t next_frame_token() const { return *next_frame_token_; }

  // Buffers |callback| until a relevant frame swap ocurrs, at which point the
  // callback will be posted to run on the main thread. A frame swap is
  // considered relevant if the swapped frame's token is greater than or equal
  // to |frame_token|.
  void RegisterMainThreadPresentationTimeCallback(
      uint32_t frame_token,
      LayerTreeHost::PresentationTimeCallback callback);

  // Buffers |callback| until a relevant frame swap ocurrs, at which point the
  // callback will be run on the compositor thread. A frame swap is considered
  // relevant if the swapped frame's token is greater than or equal to
  // |frame_token|.
  void RegisterCompositorPresentationTimeCallback(
      uint32_t frame_token,
      LayerTreeHost::PresentationTimeCallback callback);

  virtual bool WillBeginImplFrame(const viz::BeginFrameArgs& args);
  virtual void DidFinishImplFrame(const viz::BeginFrameArgs& args);
  void DidNotProduceFrame(const viz::BeginFrameAck& ack,
                          FrameSkippedReason reason);
  void DidModifyTilePriorities();
  // Requests that we do not produce frames until the new viz::LocalSurfaceId
  // has been activated.
  void SetTargetLocalSurfaceId(
      const viz::LocalSurfaceId& target_local_surface_id);
  const viz::LocalSurfaceId& target_local_surface_id() const {
    return target_local_surface_id_;
  }
  const viz::LocalSurfaceId& last_draw_local_surface_id() const {
    return last_draw_local_surface_id_;
  }

  LayerTreeImpl* active_tree() { return active_tree_.get(); }
  const LayerTreeImpl* active_tree() const { return active_tree_.get(); }
  LayerTreeImpl* pending_tree() { return pending_tree_.get(); }
  const LayerTreeImpl* pending_tree() const { return pending_tree_.get(); }
  LayerTreeImpl* recycle_tree() { return recycle_tree_.get(); }
  const LayerTreeImpl* recycle_tree() const { return recycle_tree_.get(); }
  // Returns the tree LTH synchronizes with.
  LayerTreeImpl* sync_tree() const {
    return CommitToActiveTree() ? active_tree_.get() : pending_tree_.get();
  }
  virtual void CreatePendingTree();
  virtual void ActivateSyncTree();

  // Shortcuts to layers/nodes on the active tree.
  ScrollNode* InnerViewportScrollNode() const;
  ScrollNode* OuterViewportScrollNode() const;
  ScrollNode* CurrentlyScrollingNode();
  const ScrollNode* CurrentlyScrollingNode() const;

  void QueueSwapPromiseForMainThreadScrollUpdate(
      std::unique_ptr<SwapPromise> swap_promise);

  // TODO(bokan): These input-related methods shouldn't be part of
  // LayerTreeHostImpl's interface.
  bool IsPinchGestureActive() const;
  // See comment in equivalent ThreadedInputHandler method for what this means.
  ActivelyScrollingType GetActivelyScrollingType() const;
  bool ScrollAffectsScrollHandler() const;
  void SetExternalPinchGestureActive(bool active);
  void set_force_smooth_wheel_scrolling_for_testing(bool enabled) {
    GetInputHandler().set_force_smooth_wheel_scrolling_for_testing(enabled);
  }

  virtual void SetVisible(bool visible);
  bool visible() const { return visible_; }

  void SetNeedsOneBeginImplFrame();
  void SetNeedsRedraw();

  ManagedMemoryPolicy ActualManagedMemoryPolicy() const;

  const gfx::Transform& DrawTransform() const;

  // During commit, processes and returns changes in the compositor since the
  // last commit.
  std::unique_ptr<CompositorCommitData> ProcessCompositorDeltas();

  DroppedFrameCounter* dropped_frame_counter() {
    return &dropped_frame_counter_;
  }
  MemoryHistory* memory_history() { return memory_history_.get(); }
  DebugRectHistory* debug_rect_history() { return debug_rect_history_.get(); }
  viz::ClientResourceProvider* resource_provider() {
    return &resource_provider_;
  }
  BrowserControlsOffsetManager* browser_controls_manager() {
    return browser_controls_offset_manager_.get();
  }
  const GlobalStateThatImpactsTilePriority& global_tile_state() {
    return global_tile_state_;
  }

  TaskRunnerProvider* task_runner_provider() const {
    return task_runner_provider_;
  }

  MutatorHost* mutator_host() const { return mutator_host_.get(); }

  void SetDebugState(const LayerTreeDebugState& new_debug_state);
  const LayerTreeDebugState& debug_state() const { return debug_state_; }

  void SetTreePriority(TreePriority priority);
  TreePriority GetTreePriority() const;

  // TODO(mithro): Remove this methods which exposes the internal
  // viz::BeginFrameArgs to external callers.
  virtual const viz::BeginFrameArgs& CurrentBeginFrameArgs() const;

  // Expected time between two begin impl frame calls.
  base::TimeDelta CurrentBeginFrameInterval() const;

  void AsValueWithFrameInto(FrameData* frame,
                            base::trace_event::TracedValue* value) const;
  std::unique_ptr<base::trace_event::ConvertableToTraceFormat> AsValueWithFrame(
      FrameData* frame) const;
  void ActivationStateAsValueInto(base::trace_event::TracedValue* value) const;

  bool page_scale_animation_active() const { return !!page_scale_animation_; }

  virtual void CreateUIResource(UIResourceId uid,
                                const UIResourceBitmap& bitmap);
  // Deletes a UI resource.  May safely be called more than once.
  virtual void DeleteUIResource(UIResourceId uid);
  // Evict all UI resources. This differs from ClearUIResources in that this
  // will not immediately delete the resources' backing textures.
  void EvictAllUIResources();
  bool EvictedUIResourcesExist() const;

  virtual viz::ResourceId ResourceIdForUIResource(UIResourceId uid) const;

  virtual bool IsUIResourceOpaque(UIResourceId uid) const;

  void ScheduleMicroBenchmark(std::unique_ptr<MicroBenchmarkImpl> benchmark);

  viz::CompositorFrameMetadata MakeCompositorFrameMetadata();
  RenderFrameMetadata MakeRenderFrameMetadata(FrameData* frame);

  const gfx::Rect& external_viewport() const { return external_viewport_; }

  // Viewport rect to be used for tiling prioritization instead of the
  // DeviceViewport().
  const gfx::Rect& viewport_rect_for_tile_priority() const {
    return viewport_rect_for_tile_priority_;
  }

  // When a SwapPromiseMonitor is created on the impl thread, it calls
  // InsertSwapPromiseMonitor() to register itself with LayerTreeHostImpl.
  // When the monitor is destroyed, it calls RemoveSwapPromiseMonitor()
  // to unregister itself.
  void InsertSwapPromiseMonitor(SwapPromiseMonitor* monitor);
  void RemoveSwapPromiseMonitor(SwapPromiseMonitor* monitor);

  // TODO(weiliangc): Replace RequiresHighResToDraw with scheduler waits for
  // ReadyToDraw. crbug.com/469175
  void SetRequiresHighResToDraw() { requires_high_res_to_draw_ = true; }
  void ResetRequiresHighResToDraw() { requires_high_res_to_draw_ = false; }
  bool RequiresHighResToDraw() const { return requires_high_res_to_draw_; }

  // Only valid for synchronous (non-scheduled) single-threaded case.
  void SynchronouslyInitializeAllTiles();

  bool CommitToActiveTree() const;

  // Virtual so tests can inject their own.
  virtual std::unique_ptr<RasterBufferProvider> CreateRasterBufferProvider();

  bool prepare_tiles_needed() const { return tile_priorities_dirty_; }

  base::SingleThreadTaskRunner* GetTaskRunner() const {
    DCHECK(task_runner_provider_);
    return task_runner_provider_->HasImplThread()
               ? task_runner_provider_->ImplThreadTaskRunner()
               : task_runner_provider_->MainThreadTaskRunner();
  }

  // Returns true if a scroll offset animation is created and false if we scroll
  // by the desired amount without an animation.
  bool ScrollAnimationCreate(const ScrollNode& scroll_node,
                             const gfx::Vector2dF& scroll_amount,
                             base::TimeDelta delayed_by);
  bool AutoScrollAnimationCreate(const ScrollNode& scroll_node,
                                 const gfx::Vector2dF& scroll_amount,
                                 float autoscroll_velocity);

  void SetLayerTreeMutator(std::unique_ptr<LayerTreeMutator> mutator);

  void SetPaintWorkletLayerPainter(
      std::unique_ptr<PaintWorkletLayerPainter> painter);
  PaintWorkletLayerPainter* GetPaintWorkletLayerPainterForTesting() const {
    return paint_worklet_painter_.get();
  }

  void QueueImageDecode(int request_id, const PaintImage& image);
  std::vector<std::pair<int, bool>> TakeCompletedImageDecodeRequests();
  // Returns mutator events to be handled by BeginMainFrame.
  std::unique_ptr<MutatorEvents> TakeMutatorEvents();

  // Returns all of the transition request sequence ids that were finished.
  std::vector<uint32_t> TakeFinishedTransitionRequestSequenceIds();

  void ClearCaches();

  void UpdateImageDecodingHints(
      base::flat_map<PaintImage::Id, PaintImage::DecodingMode>
          decoding_mode_map);

  void InitializeUkm(std::unique_ptr<ukm::UkmRecorder> recorder);
  UkmManager* ukm_manager() { return ukm_manager_.get(); }

  ActiveFrameSequenceTrackers FrameSequenceTrackerActiveTypes() {
    return frame_trackers_.FrameSequenceTrackerActiveTypes();
  }

  void RenewTreePriorityForTesting() { client_->RenewTreePriority(); }

  void SetRenderFrameObserver(
      std::unique_ptr<RenderFrameMetadataObserver> observer);

  void SetActiveURL(const GURL& url, ukm::SourceId source_id);

  void SetUkmSmoothnessDestination(
      base::WritableSharedMemoryMapping ukm_smoothness_data);

  // Notifies FrameTrackers, impl side callbacks that the compsitor frame
  // was presented.
  void NotifyDidPresentCompositorFrameOnImplThread(
      uint32_t frame_token,
      std::vector<LayerTreeHost::PresentationTimeCallback> callbacks,
      const viz::FrameTimingDetails& details);

  CompositorFrameReportingController* compositor_frame_reporting_controller()
      const {
    return compositor_frame_reporting_controller_.get();
  }

  void set_pending_tree_fully_painted_for_testing(bool painted) {
    pending_tree_fully_painted_ = painted;
  }
  AnimatedPaintWorkletTracker& paint_worklet_tracker() {
    return paint_worklet_tracker_;
  }

  bool can_use_msaa() const { return can_use_msaa_; }

  Viewport& viewport() const { return *viewport_.get(); }

  TotalFrameCounter* total_frame_counter_for_testing() {
    return &total_frame_counter_;
  }
  DroppedFrameCounter* dropped_frame_counter_for_testing() {
    return &dropped_frame_counter_;
  }

  // Returns true if the client is currently compositing synchronously.
  bool IsInSynchronousComposite() const {
    return client_->IsInSynchronousComposite();
  }

  RasterQueryQueue* GetRasterQueryQueueForTesting() const {
    return pending_raster_queries_.get();
  }

  base::flat_set<viz::FrameSinkId> GetFrameSinksToThrottleForTesting() const {
    return throttle_decider_.ids();
  }

 protected:
  LayerTreeHostImpl(
      const LayerTreeSettings& settings,
      LayerTreeHostImplClient* client,
      TaskRunnerProvider* task_runner_provider,
      RenderingStatsInstrumentation* rendering_stats_instrumentation,
      TaskGraphRunner* task_graph_runner,
      std::unique_ptr<MutatorHost> mutator_host,
      RasterDarkModeFilter* dark_mode_filter,
      int id,
      scoped_refptr<base::SequencedTaskRunner> image_worker_task_runner,
      LayerTreeHostSchedulingClient* scheduling_client);

  // Virtual for testing.
  virtual bool AnimateLayers(base::TimeTicks monotonic_time,
                             bool is_active_tree);

  bool is_likely_to_require_a_draw() const {
    return is_likely_to_require_a_draw_;
  }

  // Removes empty or orphan RenderPasses from the frame.
  static void RemoveRenderPasses(FrameData* frame);

  LayerTreeHostImplClient* const client_;
  LayerTreeHostSchedulingClient* const scheduling_client_;
  TaskRunnerProvider* const task_runner_provider_;

  BeginFrameTracker current_begin_frame_tracker_;

  std::unique_ptr<CompositorFrameReportingController>
      compositor_frame_reporting_controller_;

 private:
  void CollectScrollbarUpdatesForCommit(
      CompositorCommitData* commit_data) const;
  bool ScrollAnimationCreateInternal(const ScrollNode& scroll_node,
                                     const gfx::Vector2dF& delta,
                                     base::TimeDelta delayed_by,
                                     absl::optional<float> autoscroll_velocity);

  void CleanUpTileManagerResources();
  void CreateTileManagerResources();
  void ReleaseTreeResources();
  void ReleaseTileResources();
  void RecreateTileResources();

  void AnimateInternal();

  // The function is called to update state on the sync tree after a commit
  // finishes or after the sync tree was created to invalidate content on the
  // impl thread.
  void UpdateSyncTreeAfterCommitOrImplSideInvalidation();

  // Returns a job map for all 'dirty' PaintWorklets, e.g. PaintWorkletInputs
  // that do not map to a PaintRecord.
  PaintWorkletJobMap GatherDirtyPaintWorklets(PaintImageIdFlatSet*) const;

  // Called when all PaintWorklet results are ready (i.e. have been painted) for
  // the current pending tree.
  void OnPaintWorkletResultsReady(PaintWorkletJobMap results);

  // Called when the pending tree has been fully painted, i.e. all required data
  // is available to raster the tree.
  void NotifyPendingTreeFullyPainted();

  // Returns true if status changed.
  bool UpdateGpuRasterizationStatus();
  void UpdateTreeResourcesForGpuRasterizationIfNeeded();

  bool AnimatePageScale(base::TimeTicks monotonic_time);
  bool AnimateScrollbars(base::TimeTicks monotonic_time);
  bool AnimateBrowserControls(base::TimeTicks monotonic_time);

  void UpdateTileManagerMemoryPolicy(const ManagedMemoryPolicy& policy);

  // Returns true if the damage rect is non-empty. This check includes damage
  // from the HUD. Should only be called when the active tree's draw properties
  // are valid and after updating the damage.
  bool HasDamage() const;

  // This function should only be called from PrepareToDraw, as DidDrawAllLayers
  // must be called if this helper function is called.  Returns DRAW_SUCCESS if
  // the frame should be drawn.
  DrawResult CalculateRenderPasses(FrameData* frame);

  void StartScrollbarFadeRecursive(LayerImpl* layer);
  void SetManagedMemoryPolicy(const ManagedMemoryPolicy& policy);

  // Once a resource is uploaded or deleted, it is no longer an evicted id, this
  // removes it from the evicted set, and updates if we're able to draw now that
  // all UIResources are valid.
  void MarkUIResourceNotEvicted(UIResourceId uid);
  // Deletes all UIResource backings, and marks all the ids as evicted.
  void ClearUIResources();
  // Frees the textures/bitmaps backing the UIResource, held in the
  // UIResourceData.
  void DeleteUIResourceBacking(UIResourceData data,
                               const gpu::SyncToken& sync_token);
  // Callback for when a UIResource is deleted *and* no longer in use by the
  // display compositor. It will DeleteUIResourceBacking() if the backing was
  // not already deleted preemptively.
  void OnUIResourceReleased(UIResourceId uid,
                            const gpu::SyncToken& sync_token,
                            bool lost);

  void NotifySwapPromiseMonitorsOfSetNeedsRedraw();

 private:
  void SetContextVisibility(bool is_visible);
  void ImageDecodeFinished(int request_id, bool decode_succeeded);

  void ShowScrollbarsForImplScroll(ElementId element_id);

  // Copy any opacity values already in the active tree to the pending
  // tree, because the active tree value always takes precedence for scrollbars.
  void PushScrollbarOpacitiesFromActiveToPending();

  // Pushes state for image animations and checkerboarded images from the
  // pending to active tree. This is called during activation when a pending
  // tree exists, and during the commit if we are committing directly to the
  // active tree.
  void ActivateStateForImages();

  void OnMemoryPressure(
      base::MemoryPressureListener::MemoryPressureLevel level);

  void AllocateLocalSurfaceId();

  // Log the AverageLag events from the frame identified by |frame_token| and
  // the information in |details|.
  void LogAverageLagEvents(uint32_t frame_token,
                           const viz::FrameTimingDetails& details);

  // Notifies client about the custom tracker results.
  void NotifyThroughputTrackerResults(const CustomTrackerResults& results);

  // Wrapper for checking and updating |contains_srgb_cache_|.
  bool CheckColorSpaceContainsSrgb(const gfx::ColorSpace& color_space) const;

  // Once bound, this instance owns the InputHandler. However, an InputHandler
  // need not be bound so this should be null-checked before dereferencing.
  std::unique_ptr<InputDelegateForCompositor> input_delegate_;

  const LayerTreeSettings settings_;

  // This is set to true only if:
  //  . The compositor is running single-threaded (i.e. there is no separate
  //    compositor/impl thread).
  //  . There is no scheduler (which means layer-update, composite, etc. steps
  //    happen explicitly via. synchronous calls to appropriate functions).
  // This is usually turned on only in some tests (e.g. web-tests).
  const bool is_synchronous_single_threaded_;

  viz::ClientResourceProvider resource_provider_;

  std::unordered_map<UIResourceId, UIResourceData> ui_resource_map_;
  // UIResources are held here once requested to be deleted until they are
  // released from the display compositor, then the backing can be deleted.
  std::unordered_map<UIResourceId, UIResourceData> deleted_ui_resources_;
  // Resources that were evicted by EvictAllUIResources. Resources are removed
  // from this when they are touched by a create or destroy from the UI resource
  // request queue. The resource IDs held in here do not have any backing
  // associated with them anymore, as that is freed at the time of eviction.
  std::set<UIResourceId> evicted_ui_resources_;

  // These are valid when has_valid_layer_tree_frame_sink_ is true.
  //
  // A pointer used for communicating with and submitting output to the display
  // compositor.
  LayerTreeFrameSink* layer_tree_frame_sink_ = nullptr;
  // The maximum size (either width or height) that any texture can be. Also
  // holds a reasonable value for software compositing bitmaps.
  int max_texture_size_ = 0;

  // The following scoped variables must not outlive the
  // |layer_tree_frame_sink_|.
  // These should be transfered to viz::ContextCacheController's
  // ClientBecameNotVisible() before the output surface is destroyed.
  std::unique_ptr<viz::ContextCacheController::ScopedVisibility>
      compositor_context_visibility_;
  std::unique_ptr<viz::ContextCacheController::ScopedVisibility>
      worker_context_visibility_;

  bool can_use_msaa_ = false;
  bool supports_disable_msaa_ = false;

  bool need_update_gpu_rasterization_status_ = false;
  bool use_gpu_rasterization_ = false;
  bool can_use_oop_rasterization_ = false;
  GpuRasterizationStatus gpu_rasterization_status_ =
      GpuRasterizationStatus::OFF_DEVICE;
  std::unique_ptr<RasterBufferProvider> raster_buffer_provider_;
  std::unique_ptr<ResourcePool> resource_pool_;
  std::unique_ptr<RasterQueryQueue> pending_raster_queries_;
  std::unique_ptr<ImageDecodeCache> image_decode_cache_;

  GlobalStateThatImpactsTilePriority global_tile_state_;

  // Tree currently being drawn.
  std::unique_ptr<LayerTreeImpl> active_tree_;

  // In impl-side painting mode, tree with possibly incomplete rasterized
  // content. May be promoted to active by ActivateSyncTree().
  std::unique_ptr<LayerTreeImpl> pending_tree_;

  // In impl-side painting mode, inert tree with layers that can be recycled
  // by the next sync from the main thread.
  std::unique_ptr<LayerTreeImpl> recycle_tree_;

  // Tracks, for debugging purposes, the amount of scroll received (not
  // necessarily applied) in this compositor frame. This will be reset each
  // time a CompositorFrame is generated.
  gfx::Vector2dF scroll_accumulated_this_frame_;

  std::vector<std::unique_ptr<SwapPromise>>
      swap_promises_for_main_thread_scroll_update_;

  bool tile_priorities_dirty_ = false;

  LayerTreeDebugState debug_state_;
  bool visible_ = false;
  ManagedMemoryPolicy cached_managed_memory_policy_;

  TileManager tile_manager_;

  std::unique_ptr<BrowserControlsOffsetManager>
      browser_controls_offset_manager_;

  std::unique_ptr<PageScaleAnimation> page_scale_animation_;

  DroppedFrameCounter dropped_frame_counter_;
  TotalFrameCounter total_frame_counter_;

  std::unique_ptr<MemoryHistory> memory_history_;
  std::unique_ptr<DebugRectHistory> debug_rect_history_;

  // The maximum memory that would be used by the prioritized resource
  // manager, if there were no limit on memory usage.
  size_t max_memory_needed_bytes_ = 0;

  // Optional top-level constraints that can be set by the LayerTreeFrameSink.
  // - external_transform_ applies a transform above the root layer
  // - external_viewport_ is used DrawProperties, tile management and
  // glViewport/window projection matrix.
  // - viewport_rect_for_tile_priority_ is the rect in view space used for
  // tiling priority.
  gfx::Transform external_transform_;
  gfx::Rect external_viewport_;
  gfx::Rect viewport_rect_for_tile_priority_;
  bool resourceless_software_draw_ = false;

  gfx::Rect viewport_damage_rect_;

  std::unique_ptr<MutatorHost> mutator_host_;
  std::unique_ptr<MutatorEvents> mutator_events_;
  std::set<VideoFrameController*> video_frame_controllers_;
  RasterDarkModeFilter* const dark_mode_filter_;

  // Map from scroll element ID to scrollbar animation controller.
  // There is one animation controller per pair of overlay scrollbars.
  std::unordered_map<ElementId,
                     std::unique_ptr<ScrollbarAnimationController>,
                     ElementIdHash>
      scrollbar_animation_controllers_;

  RenderingStatsInstrumentation* rendering_stats_instrumentation_;
  MicroBenchmarkControllerImpl micro_benchmark_controller_;
  std::unique_ptr<SynchronousTaskGraphRunner>
      single_thread_synchronous_task_graph_runner_;

  // Optional callback to notify of new tree activations.
  base::RepeatingClosure tree_activation_callback_;

  TaskGraphRunner* task_graph_runner_;
  int id_;

  std::set<SwapPromiseMonitor*> swap_promise_monitor_;

  bool requires_high_res_to_draw_ = false;
  bool is_likely_to_require_a_draw_ = false;

  // TODO(danakj): Delete the LayerTreeFrameSink and all resources when
  // it's lost instead of having this bool.
  bool has_valid_layer_tree_frame_sink_ = false;

  // If it is enabled in the LayerTreeSettings, we can check damage in
  // WillBeginImplFrame and abort early if there is no damage. We only check
  // damage in WillBeginImplFrame if a recent frame had no damage. We keep
  // track of this with |consecutive_frame_with_damage_count_|.
  int consecutive_frame_with_damage_count_;

  std::unique_ptr<Viewport> viewport_;

  gfx::Size visual_device_viewport_size_;
  // Set to true if viewport is mobile optimized by using meta tag
  // <meta name="viewport" content="width=device-width">
  // or
  // <meta name="viewport" content="initial-scale=1.0">
  bool is_viewport_mobile_optimized_ = false;

  std::unique_ptr<PendingTreeRasterDurationHistogramTimer>
      pending_tree_raster_duration_timer_;

  // These completion states to be transfered to the main thread when we
  // begin main frame. The pair represents a request id and the completion (ie
  // success) state.
  std::vector<std::pair<int, bool>> completed_image_decode_requests_;

  enum class ImplThreadPhase {
    IDLE,
    INSIDE_IMPL_FRAME,
  };
  ImplThreadPhase impl_thread_phase_ = ImplThreadPhase::IDLE;

  ImageAnimationController image_animation_controller_;

  std::unique_ptr<UkmManager> ukm_manager_;

  // Provides RenderFrameMetadata to the Browser process upon the submission of
  // each CompositorFrame.
  std::unique_ptr<RenderFrameMetadataObserver> render_frame_metadata_observer_;

  viz::FrameTokenGenerator next_frame_token_;

  viz::LocalSurfaceId last_draw_local_surface_id_;
  base::flat_set<viz::SurfaceRange> last_draw_referenced_surfaces_;
  absl::optional<RenderFrameMetadata> last_draw_render_frame_metadata_;
  // The viz::LocalSurfaceId to unthrottle drawing for.
  viz::LocalSurfaceId target_local_surface_id_;
  viz::ChildLocalSurfaceIdAllocator child_local_surface_id_allocator_;

  // Indicates the direction of the last vertical scroll of the root layer.
  // Until the first vertical scroll occurs, this value is |kNull|. Note that
  // once this value is updated, it will never return to |kNull|.
  viz::VerticalScrollDirection last_vertical_scroll_direction_ =
      viz::VerticalScrollDirection::kNull;

  std::unique_ptr<base::MemoryPressureListener> memory_pressure_listener_;

  PresentationTimeCallbackBuffer presentation_time_callbacks_;

  const PaintImage::GeneratorClientId paint_image_generator_client_id_;

  FrameSequenceTrackerCollection frame_trackers_;

  // PaintWorklet painting is controlled from the LayerTreeHostImpl, dispatched
  // to the worklet thread via |paint_worklet_painter_|.
  std::unique_ptr<PaintWorkletLayerPainter> paint_worklet_painter_;

  // While PaintWorklet painting is ongoing the PendingTree is not yet fully
  // painted and cannot be rastered or activated. This boolean tracks whether or
  // not we are in that state.
  bool pending_tree_fully_painted_ = false;

#if DCHECK_IS_ON()
  // Use to track when doing a synchronous draw.
  bool doing_sync_draw_ = false;
#endif

  // This is used to tell the scheduler there are active scroll handlers on the
  // page so we should prioritize latency during a scroll to try to keep
  // scroll-linked effects up to data.
  // TODO(bokan): This is quite old and scheduling has become much more
  // sophisticated since so it's not clear how much value it's still providing.
  bool scroll_affects_scroll_handler_ = false;

  // Provides support for PaintWorklets which depend on input properties that
  // are being animated by the compositor (aka 'animated' PaintWorklets).
  // Responsible for storing animated custom property values and for
  // invalidating PaintWorklets as the property values change.
  AnimatedPaintWorkletTracker paint_worklet_tracker_;

  AverageLagTrackingManager lag_tracking_manager_;

  // Helper for de-jelly logic.
  DeJellyState de_jelly_state_;

  EventsMetricsManager events_metrics_manager_;

  std::unique_ptr<LCDTextMetricsReporter> lcd_text_metrics_reporter_;

  FrameRateEstimator frame_rate_estimator_;
  bool has_observed_first_scroll_delay_ = false;

  bool enable_frame_rate_throttling_ = false;

  // True if we are measuring smoothness in TotalFrameCounter and
  // DroppedFrameCounter. Currently true when first contentful paint is done.
  bool is_measuring_smoothness_ = false;

  base::WritableSharedMemoryMapping ukm_smoothness_mapping_;

  // Cache for the results of calls to gfx::ColorSpace::Contains() on sRGB. This
  // computation is deterministic for a given color space, can be called
  // multiple times per frame, and incurs a non-trivial cost.
  // mutable because |contains_srgb_cache_| is accessed in a const method.
  mutable base::MRUCache<gfx::ColorSpace, bool> contains_srgb_cache_;

  // When enabled, calculates which frame sinks can be throttled based on
  // some pre-defined criteria.
  ThrottleDecider throttle_decider_;

  std::vector<uint32_t> finished_transition_request_sequence_ids_;

  // Must be the last member to ensure this is destroyed first in the
  // destruction order and invalidates all weak pointers.
  base::WeakPtrFactory<LayerTreeHostImpl> weak_factory_{this};
};

}  // namespace cc

#endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_