layer_tree_host.cc

// 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.h"

#include <stddef.h>
#include <stdint.h>

#include <algorithm>
#include <memory>
#include <string>
#include <unordered_map>

#include "base/atomic_sequence_num.h"
#include "base/auto_reset.h"
#include "base/bind.h"
#include "base/command_line.h"
#include "base/containers/adapters.h"
#include "base/containers/contains.h"
#include "base/location.h"
#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "base/metrics/histogram_functions.h"
#include "base/metrics/histogram_macros.h"
#include "base/numerics/safe_math.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/stringprintf.h"
#include "base/task/single_thread_task_runner.h"
#include "base/threading/thread_task_runner_handle.h"
#include "base/timer/elapsed_timer.h"
#include "base/trace_event/trace_event.h"
#include "base/trace_event/traced_value.h"
#include "build/build_config.h"
#include "cc/base/devtools_instrumentation.h"
#include "cc/base/features.h"
#include "cc/base/histograms.h"
#include "cc/base/math_util.h"
#include "cc/debug/rendering_stats_instrumentation.h"
#include "cc/document_transition/document_transition_request.h"
#include "cc/input/layer_selection_bound.h"
#include "cc/input/overscroll_behavior.h"
#include "cc/input/page_scale_animation.h"
#include "cc/layers/heads_up_display_layer.h"
#include "cc/layers/heads_up_display_layer_impl.h"
#include "cc/layers/layer.h"
#include "cc/layers/painted_scrollbar_layer.h"
#include "cc/metrics/ukm_smoothness_data.h"
#include "cc/paint/paint_worklet_layer_painter.h"
#include "cc/resources/ui_resource_manager.h"
#include "cc/tiles/raster_dark_mode_filter.h"
#include "cc/trees/clip_node.h"
#include "cc/trees/commit_state.h"
#include "cc/trees/compositor_commit_data.h"
#include "cc/trees/draw_property_utils.h"
#include "cc/trees/effect_node.h"
#include "cc/trees/layer_tree_host_client.h"
#include "cc/trees/layer_tree_host_impl.h"
#include "cc/trees/layer_tree_impl.h"
#include "cc/trees/mobile_optimized_viewport_util.h"
#include "cc/trees/mutator_host.h"
#include "cc/trees/paint_holding_reason.h"
#include "cc/trees/property_tree_builder.h"
#include "cc/trees/proxy_main.h"
#include "cc/trees/render_frame_metadata_observer.h"
#include "cc/trees/scroll_node.h"
#include "cc/trees/single_thread_proxy.h"
#include "cc/trees/swap_promise_manager.h"
#include "cc/trees/transform_node.h"
#include "cc/trees/tree_synchronizer.h"
#include "cc/trees/ukm_manager.h"
#include "components/viz/common/features.h"
#include "services/metrics/public/cpp/ukm_recorder.h"
#include "services/tracing/public/cpp/perfetto/flow_event_utils.h"
#include "services/tracing/public/cpp/perfetto/macros.h"
#include "ui/gfx/geometry/size_conversions.h"
#include "ui/gfx/geometry/vector2d_conversions.h"
#include "ui/gfx/presentation_feedback.h"

namespace {
static base::AtomicSequenceNumber s_layer_tree_host_sequence_number;
static base::AtomicSequenceNumber s_image_decode_sequence_number;
}  // namespace

namespace cc {
namespace {

bool AreEmbedTokensEqual(const viz::LocalSurfaceId& lsi1,
                         const viz::LocalSurfaceId& lsi2) {
  return lsi1.embed_token() == lsi2.embed_token();
}

bool AreParentSequencesEqual(const viz::LocalSurfaceId& lsi1,
                             const viz::LocalSurfaceId& lsi2) {
  return lsi1.parent_sequence_number() == lsi2.parent_sequence_number();
}

}  // namespace

LayerTreeHost::InitParams::InitParams() = default;
LayerTreeHost::InitParams::~InitParams() = default;
LayerTreeHost::InitParams::InitParams(InitParams&&) = default;
LayerTreeHost::InitParams& LayerTreeHost::InitParams::operator=(InitParams&&) =
    default;

LayerTreeHost::ScrollAnimationState::ScrollAnimationState() = default;
LayerTreeHost::ScrollAnimationState::~ScrollAnimationState() = default;

std::unique_ptr<LayerTreeHost> LayerTreeHost::CreateThreaded(
    scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner,
    InitParams params) {
  DCHECK(params.settings);
  scoped_refptr<base::SingleThreadTaskRunner> main_task_runner =
      params.main_task_runner;
  DCHECK(main_task_runner);
  DCHECK(impl_task_runner);
  auto layer_tree_host = base::WrapUnique(
      new LayerTreeHost(std::move(params), CompositorMode::THREADED));
  layer_tree_host->InitializeThreaded(std::move(main_task_runner),
                                      std::move(impl_task_runner));
  return layer_tree_host;
}

std::unique_ptr<LayerTreeHost> LayerTreeHost::CreateSingleThreaded(
    LayerTreeHostSingleThreadClient* single_thread_client,
    InitParams params) {
  DCHECK(params.settings);
  scoped_refptr<base::SingleThreadTaskRunner> main_task_runner =
      params.main_task_runner;
  auto layer_tree_host = base::WrapUnique(
      new LayerTreeHost(std::move(params), CompositorMode::SINGLE_THREADED));
  layer_tree_host->InitializeSingleThreaded(single_thread_client,
                                            std::move(main_task_runner));
  return layer_tree_host;
}

LayerTreeHost::LayerTreeHost(InitParams params, CompositorMode mode)
    : micro_benchmark_controller_(this),
      image_worker_task_runner_(std::move(params.image_worker_task_runner)),
      ukm_recorder_factory_(std::move(params.ukm_recorder_factory)),
      compositor_mode_(mode),
      ui_resource_manager_(std::make_unique<UIResourceManager>()),
      client_(params.client),
      scheduling_client_(params.scheduling_client),
      rendering_stats_instrumentation_(RenderingStatsInstrumentation::Create()),
      pending_commit_state_(std::make_unique<CommitState>()),
      settings_(*params.settings),
      id_(s_layer_tree_host_sequence_number.GetNext() + 1),
      task_graph_runner_(params.task_graph_runner),
      main_thread_pipeline_(params.main_thread_pipeline),
      compositor_thread_pipeline_(params.compositor_thread_pipeline),
      mutator_host_(params.mutator_host),
      dark_mode_filter_(params.dark_mode_filter) {
  DCHECK(task_graph_runner_);
  DCHECK(!settings_.enable_checker_imaging || image_worker_task_runner_);

  pending_commit_state_->needs_gpu_rasterization_histogram =
      (mode == CompositorMode::THREADED);
  pending_commit_state_->needs_full_tree_sync = true;
  pending_commit_state_->debug_state = settings_.initial_debug_state;

  mutator_host_->SetMutatorHostClient(this);

  rendering_stats_instrumentation_->set_record_rendering_stats(
      pending_commit_state_->debug_state.RecordRenderingStats());
}

bool LayerTreeHost::IsMobileOptimized() const {
  gfx::SizeF scrollable_viewport_size;
  auto* inner_node = property_trees()->scroll_tree.Node(
      pending_commit_state()->viewport_property_ids.inner_scroll);
  if (!inner_node)
    scrollable_viewport_size = gfx::SizeF();
  else
    scrollable_viewport_size = gfx::ScaleSize(
        gfx::SizeF(inner_node->container_bounds),
        1.0f / (pending_commit_state()->external_page_scale_factor *
                page_scale_factor()));

  gfx::SizeF scrollable_size;
  auto* scroll_node = property_trees()->scroll_tree.Node(
      pending_commit_state()->viewport_property_ids.outer_scroll);
  if (!scroll_node) {
    DCHECK(!inner_node);
    scrollable_size = gfx::SizeF();
  } else {
    const auto& scroll_tree = property_trees()->scroll_tree;
    auto size = scroll_tree.scroll_bounds(scroll_node->id);
    size.SetToMax(gfx::SizeF(scroll_tree.container_bounds(scroll_node->id)));
    scrollable_size = size;
  }

  return util::IsMobileOptimized(
      min_page_scale_factor(), max_page_scale_factor(), page_scale_factor(),
      scrollable_viewport_size, scrollable_size,
      pending_commit_state()->is_viewport_mobile_optimized);
}

void LayerTreeHost::InitializeThreaded(
    scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
    scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner) {
  task_runner_provider_ =
      TaskRunnerProvider::Create(main_task_runner, impl_task_runner);
  std::unique_ptr<ProxyMain> proxy_main =
      std::make_unique<ProxyMain>(this, task_runner_provider_.get());
  InitializeProxy(std::move(proxy_main));
}

void LayerTreeHost::InitializeSingleThreaded(
    LayerTreeHostSingleThreadClient* single_thread_client,
    scoped_refptr<base::SingleThreadTaskRunner> main_task_runner) {
  task_runner_provider_ = TaskRunnerProvider::Create(main_task_runner, nullptr);
  InitializeProxy(SingleThreadProxy::Create(this, single_thread_client,
                                            task_runner_provider_.get()));
}

void LayerTreeHost::InitializeForTesting(
    std::unique_ptr<TaskRunnerProvider> task_runner_provider,
    std::unique_ptr<Proxy> proxy_for_testing) {
  task_runner_provider_ = std::move(task_runner_provider);
  InitializeProxy(std::move(proxy_for_testing));
}

void LayerTreeHost::SetTaskRunnerProviderForTesting(
    std::unique_ptr<TaskRunnerProvider> task_runner_provider) {
  DCHECK(!task_runner_provider_);
  task_runner_provider_ = std::move(task_runner_provider);
}

void LayerTreeHost::SetUIResourceManagerForTesting(
    std::unique_ptr<UIResourceManager> ui_resource_manager) {
  ui_resource_manager_ = std::move(ui_resource_manager);
}

void LayerTreeHost::InitializeProxy(std::unique_ptr<Proxy> proxy) {
  TRACE_EVENT0("cc", "LayerTreeHost::InitializeForReal");
  DCHECK(task_runner_provider_);

  proxy_ = std::move(proxy);
  proxy_->Start();

  UpdateDeferMainFrameUpdateInternal();
}

LayerTreeHost::~LayerTreeHost() {
  // Track when we're inside a main frame to see if compositor is being
  // destroyed midway which causes a crash. crbug.com/895883
  CHECK(!inside_main_frame_);
  DCHECK(!in_commit());
  TRACE_EVENT0("cc", "LayerTreeHost::~LayerTreeHost");

  // Clear any references into the LayerTreeHost.
  mutator_host_->SetMutatorHostClient(nullptr);

  if (root_layer()) {
    root_layer()->SetLayerTreeHost(nullptr);

    // The root layer must be destroyed before the layer tree. We've made a
    // contract with our animation controllers that the animation_host will
    // outlive them, and we must make good.
    pending_commit_state()->root_layer = nullptr;
  }

  // Fail any pending image decodes.
  for (auto& pair : pending_image_decodes_)
    std::move(pair.second).Run(false);

  if (proxy_) {
    DCHECK(task_runner_provider_->IsMainThread());
    proxy_->Stop();

    // Proxy must be destroyed before the Task Runner Provider.
    proxy_ = nullptr;
  }
}

int LayerTreeHost::GetId() const {
  return id_;
}

int LayerTreeHost::SourceFrameNumber() const {
  DCHECK(task_runner_provider_->IsMainThread());
  return pending_commit_state()->source_frame_number;
}

UIResourceManager* LayerTreeHost::GetUIResourceManager() {
  return ui_resource_manager_.get();
}

TaskRunnerProvider* LayerTreeHost::GetTaskRunnerProvider() {
  return task_runner_provider_.get();
}

SwapPromiseManager* LayerTreeHost::GetSwapPromiseManager() {
  return &swap_promise_manager_;
}

std::unique_ptr<EventsMetricsManager::ScopedMonitor>
LayerTreeHost::GetScopedEventMetricsMonitor(
    EventsMetricsManager::ScopedMonitor::DoneCallback done_callback) {
  return events_metrics_manager_.GetScopedMonitor(std::move(done_callback));
}

void LayerTreeHost::ClearEventsMetrics() {
  // Take events metrics and drop them.
  events_metrics_manager_.TakeSavedEventsMetrics();
}

const LayerTreeSettings& LayerTreeHost::GetSettings() const {
  return settings_;
}

void LayerTreeHost::QueueSwapPromise(
    std::unique_ptr<SwapPromise> swap_promise) {
  swap_promise_manager_.QueueSwapPromise(std::move(swap_promise));
}

void LayerTreeHost::WillBeginMainFrame() {
  inside_main_frame_ = true;
  devtools_instrumentation::WillBeginMainThreadFrame(GetId(),
                                                     SourceFrameNumber());
  client_->WillBeginMainFrame();
}

void LayerTreeHost::DidBeginMainFrame() {
  inside_main_frame_ = false;
  client_->DidBeginMainFrame();
}

void LayerTreeHost::BeginMainFrameNotExpectedSoon() {
  client_->BeginMainFrameNotExpectedSoon();
}

void LayerTreeHost::BeginMainFrameNotExpectedUntil(base::TimeTicks time) {
  client_->BeginMainFrameNotExpectedUntil(time);
}

void LayerTreeHost::BeginMainFrame(const viz::BeginFrameArgs& args) {
  client_->BeginMainFrame(args);
}

const LayerTreeDebugState& LayerTreeHost::GetDebugState() const {
  return pending_commit_state()->debug_state;
}

void LayerTreeHost::RequestMainFrameUpdate(bool report_metrics) {
  client_->UpdateLayerTreeHost();
  if (report_metrics)
    pending_commit_state()->begin_main_frame_metrics =
        client_->GetBeginMainFrameMetrics();
  else
    pending_commit_state()->begin_main_frame_metrics.reset();
}

// This function commits the LayerTreeHost to an impl tree. When modifying
// this function, keep in mind that the function *runs* on the impl thread! Any
// code that is logically a main thread operation, e.g. deletion of a Layer,
// should be delayed until the LayerTreeHost::CommitComplete, which will run
// after the commit, but on the main thread.
void LayerTreeHost::FinishCommitOnImplThread(LayerTreeHostImpl* host_impl) {
  DCHECK(task_runner_provider_->IsImplThread());
  CommitState* state = active_commit_state();
  DCHECK(state);

  TRACE_EVENT0("cc,benchmark", "LayerTreeHost::FinishCommitOnImplThread");

  LayerTreeImpl* sync_tree = host_impl->sync_tree();
  sync_tree->lifecycle().AdvanceTo(LayerTreeLifecycle::kBeginningSync);

  if (state->next_commit_forces_redraw)
    sync_tree->ForceRedrawNextActivation();
  if (state->next_commit_forces_recalculate_raster_scales)
    sync_tree->ForceRecalculateRasterScales();
  if (!state->pending_presentation_time_callbacks.empty()) {
    sync_tree->AddPresentationCallbacks(
        std::move(state->pending_presentation_time_callbacks));
  }

  if (state->needs_full_tree_sync)
    TreeSynchronizer::SynchronizeTrees(state, sync_tree);

  if (state->clear_caches_on_next_commit) {
    proxy_->ClearHistory();
    host_impl->ClearCaches();
  }

  {
    TRACE_EVENT0("cc", "LayerTreeHost::PushProperties");

    PushPropertyTreesTo(sync_tree);
    sync_tree->lifecycle().AdvanceTo(LayerTreeLifecycle::kSyncedPropertyTrees);

    if (state->needs_surface_ranges_sync) {
      sync_tree->ClearSurfaceRanges();
      sync_tree->SetSurfaceRanges(state->SurfaceRanges());
    }
    TreeSynchronizer::PushLayerProperties(state, sync_tree);
    sync_tree->lifecycle().AdvanceTo(
        LayerTreeLifecycle::kSyncedLayerProperties);

    PushLayerTreePropertiesTo(state, sync_tree);
    PushLayerTreeHostPropertiesTo(host_impl);

    sync_tree->PassSwapPromises(std::move(state->swap_promises));
    sync_tree->AppendEventsMetricsFromMainThread(
        std::move(state->event_metrics));

    sync_tree->set_ui_resource_request_queue(state->ui_resource_request_queue);

    // This must happen after synchronizing property trees and after pushing
    // properties, which updates the clobber_active_value flag.
    // TODO(pdr): Enforce this comment with DCHECKS and a lifecycle state.
    sync_tree->property_trees()->scroll_tree.PushScrollUpdatesFromMainThread(
        property_trees(), sync_tree, settings_.commit_fractional_scroll_deltas);

    // This must happen after synchronizing property trees and after push
    // properties, which updates property tree indices, but before animation
    // host pushes properties as animation host push properties can change
    // KeyframeModel::InEffect and we want the old InEffect value for updating
    // property tree scrolling and animation.
    // TODO(pdr): Enforce this comment with DCHECKS and a lifecycle state.
    sync_tree->UpdatePropertyTreeAnimationFromMainThread();

    TRACE_EVENT0("cc", "LayerTreeHost::AnimationHost::PushProperties");
    DCHECK(host_impl->mutator_host());
    mutator_host_->PushPropertiesTo(host_impl->mutator_host());
    MoveChangeTrackingToLayers(sync_tree);

    // Updating elements affects whether animations are in effect based on their
    // properties so run after pushing updated animation properties.
    host_impl->UpdateElements(ElementListType::PENDING);

    sync_tree->lifecycle().AdvanceTo(LayerTreeLifecycle::kNotSyncing);
  }

  // Transfer image decode requests to the impl thread.
  for (auto& entry : state->queued_image_decodes) {
    host_impl->QueueImageDecode(entry.first, *entry.second);
  }

  for (auto& benchmark : state->benchmarks)
    host_impl->ScheduleMicroBenchmark(std::move(benchmark));

  property_trees_.ResetAllChangeTracking();

  state->impl_commit_finish_time = base::TimeTicks::Now();

  // Dump property trees and layers if run with:
  //   --vmodule=layer_tree_host=3
  if (VLOG_IS_ON(3)) {
    const char* client_name = GetClientNameForMetrics();
    if (!client_name)
      client_name = "<unknown client>";
    VLOG(3) << "After finishing (" << client_name
            << ") commit on impl, the sync tree:"
            << "\nproperty_trees:\n"
            << sync_tree->property_trees()->ToString() << "\n"
            << "cc::LayerImpls:\n"
            << sync_tree->LayerListAsJson();
  }
}

void LayerTreeHost::MoveChangeTrackingToLayers(LayerTreeImpl* tree_impl) {
  // This is only true for single-thread compositing (i.e. not via Blink).
  bool property_trees_changed_on_active_tree =
      tree_impl->IsActiveTree() && tree_impl->property_trees()->changed;

  if (property_trees_changed_on_active_tree) {
    // Property trees may store damage status. We preserve the sync tree damage
    // status by pushing the damage status from sync tree property trees to main
    // thread property trees or by moving it onto the layers.
    DCHECK(active_commit_state());
    if (active_commit_state()->root_layer) {
      if (property_trees_.sequence_number ==
          tree_impl->property_trees()->sequence_number)
        tree_impl->property_trees()->PushChangeTrackingTo(&property_trees_);
      else
        tree_impl->MoveChangeTrackingToLayers();
    }
  } else {
    tree_impl->MoveChangeTrackingToLayers();
  }
}

void LayerTreeHost::ImageDecodesFinished(
    const std::vector<std::pair<int, bool>>& results) {
  // Issue stored callbacks and remove them from the pending list.
  for (const auto& pair : results) {
    auto it = pending_image_decodes_.find(pair.first);
    DCHECK(it != pending_image_decodes_.end());
    std::move(it->second).Run(pair.second);
    pending_image_decodes_.erase(it);
  }
}

void LayerTreeHost::PushPropertyTreesTo(LayerTreeImpl* tree_impl) {
  bool property_trees_changed_on_active_tree =
      tree_impl->IsActiveTree() && tree_impl->property_trees()->changed;
  // Property trees may store damage status. We preserve the sync tree damage
  // status by pushing the damage status from sync tree property trees to main
  // thread property trees or by moving it onto the layers.
  DCHECK(active_commit_state());
  if (active_commit_state()->root_layer &&
      property_trees_changed_on_active_tree) {
    if (property_trees_.sequence_number ==
        tree_impl->property_trees()->sequence_number)
      tree_impl->property_trees()->PushChangeTrackingTo(&property_trees_);
    else
      tree_impl->MoveChangeTrackingToLayers();
  }

  tree_impl->SetPropertyTrees(&property_trees_);
}

void LayerTreeHost::SetNextCommitWaitsForActivation() {
  DCHECK(task_runner_provider_->IsMainThread());
  pending_commit_state()->commit_waits_for_activation = true;
}

CommitState* LayerTreeHost::WillCommit(
    std::unique_ptr<CompletionEvent> completion,
    bool has_updates) {
  DCHECK(!commit_completion_event_);
  commit_completion_event_ = std::move(completion);
  CommitState* result = nullptr;
  if (has_updates)
    result = ActivateCommitState();
  swap_promise_manager_.WillCommit();
  client_->WillCommit(result ? result : pending_commit_state());
  pending_commit_state()->source_frame_number++;
  return result;
}

CommitState* LayerTreeHost::ActivateCommitState() {
  DCHECK(pending_commit_state());
  DCHECK(!active_commit_state_);

  // Pull state not stored directly on LayerTreeHost
  pending_commit_state()->event_metrics =
      events_metrics_manager_.TakeSavedEventsMetrics();
  pending_commit_state()->swap_promises =
      GetSwapPromiseManager()->TakeSwapPromises();
  pending_commit_state()->ui_resource_request_queue =
      ui_resource_manager_->TakeUIResourcesRequests();
  pending_commit_state()->ui_resource_sizes =
      ui_resource_manager_->GetUIResourceSizes();
  pending_commit_state()->benchmarks =
      micro_benchmark_controller_.CreateImplBenchmarks();

  active_commit_state_.swap(pending_commit_state_);
  pending_commit_state_ = std::make_unique<CommitState>(*active_commit_state_);
  return active_commit_state_.get();
}

void LayerTreeHost::WaitForCommitCompletion() {
  DCHECK(task_runner_provider_->IsMainThread());
  if (commit_completion_event_) {
    commit_completion_event_->Wait();
    commit_completion_event_ = nullptr;
  }
}

void LayerTreeHost::UpdateDeferMainFrameUpdateInternal() {
  proxy_->SetDeferMainFrameUpdate(
      defer_main_frame_update_count_ > 0 ||
      !pending_commit_state()->local_surface_id_from_parent.is_valid());
}

bool LayerTreeHost::IsUsingLayerLists() const {
  return settings_.use_layer_lists;
}

void LayerTreeHost::CommitComplete() {
  // This DCHECK ensures that WaitForCommitCompletion() will not block.
  DCHECK(!in_commit());
  WaitForCommitCompletion();
  auto* commit_state = active_commit_state_.get();
  if (commit_state) {
    client_->DidCommit(commit_state->impl_commit_start_time,
                       commit_state->impl_commit_finish_time);
  } else {
    client_->DidCommit(base::TimeTicks(), base::TimeTicks::Now());
  }
  if (did_complete_scale_animation_) {
    client_->DidCompletePageScaleAnimation();
    did_complete_scale_animation_ = false;
  }
  active_commit_state_ = nullptr;
}

void LayerTreeHost::NotifyTransitionRequestsFinished(
    const std::vector<uint32_t>& sequence_ids) {
  // TODO(vmpstr): This might also be a good spot to expire long standing
  // requests if they were not finished.
  for (auto& sequence_id : sequence_ids) {
    auto it = document_transition_callbacks_.find(sequence_id);
    if (it == document_transition_callbacks_.end())
      continue;
    std::move(it->second).Run();
    document_transition_callbacks_.erase(it);
  }
}

void LayerTreeHost::SetLayerTreeFrameSink(
    std::unique_ptr<LayerTreeFrameSink> surface) {
  TRACE_EVENT0("cc", "LayerTreeHost::SetLayerTreeFrameSink");
  DCHECK(surface);

  DCHECK(!new_layer_tree_frame_sink_);
  new_layer_tree_frame_sink_ = std::move(surface);
  proxy_->SetLayerTreeFrameSink(new_layer_tree_frame_sink_.get());
}

std::unique_ptr<LayerTreeFrameSink> LayerTreeHost::ReleaseLayerTreeFrameSink() {
  DCHECK(!visible_);

  DidLoseLayerTreeFrameSink();
  proxy_->ReleaseLayerTreeFrameSink();
  return std::move(current_layer_tree_frame_sink_);
}

void LayerTreeHost::RequestNewLayerTreeFrameSink() {
  client_->RequestNewLayerTreeFrameSink();
}

void LayerTreeHost::DidInitializeLayerTreeFrameSink() {
  DCHECK(new_layer_tree_frame_sink_);
  current_layer_tree_frame_sink_ = std::move(new_layer_tree_frame_sink_);
  client_->DidInitializeLayerTreeFrameSink();
}

void LayerTreeHost::DidFailToInitializeLayerTreeFrameSink() {
  DCHECK(new_layer_tree_frame_sink_);
  // Note: It is safe to drop all output surface references here as
  // LayerTreeHostImpl will not keep a pointer to either the old or
  // new LayerTreeFrameSink after failing to initialize the new one.
  current_layer_tree_frame_sink_ = nullptr;
  new_layer_tree_frame_sink_ = nullptr;
  client_->DidFailToInitializeLayerTreeFrameSink();
}

std::unique_ptr<LayerTreeHostImpl> LayerTreeHost::CreateLayerTreeHostImpl(
    LayerTreeHostImplClient* client) {
  DCHECK(task_runner_provider_->IsImplThread());

  std::unique_ptr<MutatorHost> mutator_host_impl =
      mutator_host_->CreateImplInstance();

  if (!settings_.scroll_animation_duration_for_testing.is_zero()) {
    mutator_host_->SetScrollAnimationDurationForTesting(
        settings_.scroll_animation_duration_for_testing);
  }

  std::unique_ptr<LayerTreeHostImpl> host_impl = LayerTreeHostImpl::Create(
      settings_, client, task_runner_provider_.get(),
      rendering_stats_instrumentation_.get(), task_graph_runner_,
      std::move(mutator_host_impl), dark_mode_filter_, id_,
      std::move(image_worker_task_runner_), scheduling_client_);
  if (ukm_recorder_factory_) {
    host_impl->InitializeUkm(ukm_recorder_factory_->CreateRecorder());
    ukm_recorder_factory_.reset();
  }

  task_graph_runner_ = nullptr;
  dark_mode_filter_ = nullptr;
  compositor_delegate_weak_ptr_ = host_impl->AsWeakPtr();
  return host_impl;
}

void LayerTreeHost::DidLoseLayerTreeFrameSink() {
  TRACE_EVENT0("cc", "LayerTreeHost::DidLoseLayerTreeFrameSink");
  DCHECK(task_runner_provider_->IsMainThread());
  SetNeedsCommit();
}

ScopedDeferMainFrameUpdate::ScopedDeferMainFrameUpdate(LayerTreeHost* host)
    : host_(host->defer_main_frame_update_weak_ptr_factory_.GetWeakPtr()) {
  host->defer_main_frame_update_count_++;
  host->UpdateDeferMainFrameUpdateInternal();
}

ScopedDeferMainFrameUpdate::~ScopedDeferMainFrameUpdate() {
  LayerTreeHost* host = host_.get();
  if (host) {
    DCHECK_GT(host->defer_main_frame_update_count_, 0u);
    if (--host->defer_main_frame_update_count_ == 0)
      host->UpdateDeferMainFrameUpdateInternal();
  }
}

std::unique_ptr<ScopedDeferMainFrameUpdate>
LayerTreeHost::DeferMainFrameUpdate() {
  return std::make_unique<ScopedDeferMainFrameUpdate>(this);
}

void LayerTreeHost::OnDeferMainFrameUpdatesChanged(bool defer_status) {
  client_->OnDeferMainFrameUpdatesChanged(defer_status);
}

bool LayerTreeHost::StartDeferringCommits(base::TimeDelta timeout,
                                          PaintHoldingReason reason) {
  return proxy_->StartDeferringCommits(timeout, reason);
}

void LayerTreeHost::StopDeferringCommits(PaintHoldingCommitTrigger trigger) {
  proxy_->StopDeferringCommits(trigger);
}

bool LayerTreeHost::IsDeferringCommits() const {
  return proxy_->IsDeferringCommits();
}

void LayerTreeHost::OnDeferCommitsChanged(bool defer_status,
                                          PaintHoldingReason reason) {
  client_->OnDeferCommitsChanged(defer_status, reason);
}

DISABLE_CFI_PERF
void LayerTreeHost::SetNeedsAnimate() {
  proxy_->SetNeedsAnimate();
  swap_promise_manager_.NotifyLatencyInfoSwapPromiseMonitors();
  events_metrics_manager_.SaveActiveEventMetrics();
}

void LayerTreeHost::SetNeedsAnimateIfNotInsideMainFrame() {
  if (!inside_main_frame_)
    SetNeedsAnimate();
}

DISABLE_CFI_PERF
void LayerTreeHost::SetNeedsUpdateLayers() {
  proxy_->SetNeedsUpdateLayers();
  swap_promise_manager_.NotifyLatencyInfoSwapPromiseMonitors();
  events_metrics_manager_.SaveActiveEventMetrics();
}

void LayerTreeHost::SetNeedsCommit() {
  proxy_->SetNeedsCommit();
  swap_promise_manager_.NotifyLatencyInfoSwapPromiseMonitors();
  events_metrics_manager_.SaveActiveEventMetrics();
}

void LayerTreeHost::SetTargetLocalSurfaceId(
    const viz::LocalSurfaceId& target_local_surface_id) {
  proxy_->SetTargetLocalSurfaceId(target_local_surface_id);
}

bool LayerTreeHost::RequestedMainFramePendingForTesting() const {
  return proxy_->RequestedAnimatePending();
}

void LayerTreeHost::SetNeedsRecalculateRasterScales() {
  pending_commit_state()->next_commit_forces_recalculate_raster_scales = true;
  proxy_->SetNeedsCommit();
}

void LayerTreeHost::SetNeedsRedrawRect(const gfx::Rect& damage_rect) {
  proxy_->SetNeedsRedraw(damage_rect);
}

bool LayerTreeHost::CommitRequested() const {
  return proxy_->CommitRequested();
}

void LayerTreeHost::SetNeedsCommitWithForcedRedraw() {
  pending_commit_state()->next_commit_forces_redraw = true;
  // This method is used by tests to ensure a commit before grabbing a screen
  // shot or processing input, so do not defer the commit.
  StopDeferringCommits(PaintHoldingCommitTrigger::kFeatureDisabled);
  proxy_->SetNeedsCommit();
}

void LayerTreeHost::SetDebugState(const LayerTreeDebugState& new_debug_state) {
  if (LayerTreeDebugState::Equal(pending_commit_state()->debug_state,
                                 new_debug_state))
    return;

  pending_commit_state()->debug_state = new_debug_state;

  rendering_stats_instrumentation_->set_record_rendering_stats(
      pending_commit_state()->debug_state.RecordRenderingStats());

  SetNeedsCommit();
}

void LayerTreeHost::ApplyPageScaleDeltaFromImplSide(float page_scale_delta) {
  DCHECK(CommitRequested());
  if (page_scale_delta == 1.f)
    return;
  float page_scale =
      pending_commit_state()->page_scale_factor * page_scale_delta;
  SetPageScaleFromImplSide(page_scale);
}

void LayerTreeHost::SetVisible(bool visible) {
  if (visible_ == visible)
    return;
  visible_ = visible;
  proxy_->SetVisible(visible);
}

bool LayerTreeHost::IsVisible() const {
  return visible_;
}

void LayerTreeHost::LayoutAndUpdateLayers() {
  DCHECK(IsSingleThreaded());
  // This function is only valid when not using the scheduler.
  DCHECK(!settings_.single_thread_proxy_scheduler);
  RequestMainFrameUpdate(false);
  UpdateLayers();
}

void LayerTreeHost::CompositeForTest(base::TimeTicks frame_begin_time,
                                     bool raster) {
  DCHECK(IsSingleThreaded());
  // This function is only valid when not using the scheduler.
  DCHECK(!settings_.single_thread_proxy_scheduler);
  SingleThreadProxy* proxy = static_cast<SingleThreadProxy*>(proxy_.get());
  proxy->CompositeImmediatelyForTest(frame_begin_time, raster);  // IN-TEST
}

bool LayerTreeHost::UpdateLayers() {
  if (!root_layer()) {
    property_trees_.clear();
    pending_commit_state()->viewport_property_ids = ViewportPropertyIds();
    return false;
  }

  DCHECK(!root_layer()->parent());
  base::ElapsedTimer timer;

  client_->WillUpdateLayers();
  bool result = DoUpdateLayers();
  client_->DidUpdateLayers();
  micro_benchmark_controller_.DidUpdateLayers();

  base::TimeDelta elapsed_delta = timer.Elapsed();
  if (pending_commit_state()->begin_main_frame_metrics) {
    pending_commit_state()->begin_main_frame_metrics->update_layers =
        elapsed_delta;
  }
  if (const char* client_name = GetClientNameForMetrics()) {
    auto elapsed = elapsed_delta.InMicroseconds();

    std::string histogram_name =
        base::StringPrintf("Compositing.%s.LayersUpdateTime", client_name);
    base::UmaHistogramCounts10M(histogram_name, elapsed);
  }

  return result;
}

void LayerTreeHost::DidPresentCompositorFrame(
    uint32_t frame_token,
    std::vector<PresentationTimeCallbackBuffer::MainCallback> callbacks,
    const gfx::PresentationFeedback& feedback) {
  for (auto& callback : callbacks)
    std::move(callback).Run(feedback);
  client_->DidPresentCompositorFrame(frame_token, feedback);
}

void LayerTreeHost::DidCompletePageScaleAnimation() {
  did_complete_scale_animation_ = true;
}

void LayerTreeHost::RecordGpuRasterizationHistogram(
    const LayerTreeHostImpl* host_impl) {
  // Gpu rasterization is only supported for Renderer compositors.
  // Checking for IsSingleThreaded() to exclude Browser compositors.
  DCHECK(active_commit_state());
  if (!active_commit_state()->needs_gpu_rasterization_histogram)
    return;

  bool gpu_rasterization_enabled = false;
  if (host_impl->layer_tree_frame_sink()) {
    viz::ContextProvider* compositor_context_provider =
        host_impl->layer_tree_frame_sink()->context_provider();
    if (compositor_context_provider) {
      gpu_rasterization_enabled =
          compositor_context_provider->ContextCapabilities().gpu_rasterization;
    }
  }

  // Record how widely gpu rasterization is enabled.
  // This number takes device/gpu allowlist/denylist into account.
  // Note that we do not consider the forced gpu rasterization mode, which is
  // mostly used for debugging purposes.
  UMA_HISTOGRAM_BOOLEAN("Renderer4.GpuRasterizationEnabled",
                        gpu_rasterization_enabled);
}

std::string LayerTreeHost::LayersAsString() const {
  std::string layers;
  for (const auto* layer : *this)
    layers += layer->ToString() + "\n";
  return layers;
}

bool LayerTreeHost::CaptureContent(std::vector<NodeInfo>* content) const {
  if (visual_device_viewport_intersection_rect_.IsEmpty())
    return false;

  gfx::Rect rect =
      gfx::Rect(visual_device_viewport_intersection_rect_.width(),
                visual_device_viewport_intersection_rect_.height());
  for (const auto* layer : *this) {
    // Normally, the node won't be drawn in multiple layers, even it is, such as
    // text strokes, the visual rect don't have too much different.
    layer->CaptureContent(rect, content);
  }
  return true;
}

void LayerTreeHost::DidObserveFirstScrollDelay(
    base::TimeDelta first_scroll_delay,
    base::TimeTicks first_scroll_timestamp) {
  client_->DidObserveFirstScrollDelay(first_scroll_delay,
                                      first_scroll_timestamp);
}

void LayerTreeHost::AddDocumentTransitionRequest(
    std::unique_ptr<DocumentTransitionRequest> request) {
  // Store the commit callback on LayerTreeHost, so that we can invoke them
  // when the request is finished.
  DCHECK(
      !base::Contains(document_transition_callbacks_, request->sequence_id()));
  document_transition_callbacks_[request->sequence_id()] =
      request->TakeFinishedCallback();
  pending_commit_state()->document_transition_requests.push_back(
      std::move(request));
  SetNeedsCommit();
}

bool LayerTreeHost::DoUpdateLayers() {
  TRACE_EVENT1("cc,benchmark", "LayerTreeHost::DoUpdateLayers",
               "source_frame_number", SourceFrameNumber());

  UpdateHudLayer(pending_commit_state()->debug_state.ShouldCreateHudLayer());

  // In layer lists mode, the cc property trees are built directly and do not
  // need to be built here.
  if (!IsUsingLayerLists()) {
    TRACE_EVENT0("cc", "LayerTreeHost::UpdateLayers::BuildPropertyTrees");
    PropertyTreeBuilder::BuildPropertyTrees(this);
    TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
                         "LayerTreeHost::UpdateLayers_BuiltPropertyTrees",
                         TRACE_EVENT_SCOPE_THREAD, "property_trees",
                         property_trees_.AsTracedValue());
  } else {
    TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
                         "LayerTreeHost::UpdateLayers_ReceivedPropertyTrees",
                         TRACE_EVENT_SCOPE_THREAD, "property_trees",
                         property_trees_.AsTracedValue());
    // The HUD layer is managed outside the layer list sent to LayerTreeHost
    // and needs to have its property tree state set.
    if (hud_layer() && root_layer()) {
      hud_layer()->SetTransformTreeIndex(root_layer()->transform_tree_index());
      hud_layer()->SetEffectTreeIndex(root_layer()->effect_tree_index());
      hud_layer()->SetClipTreeIndex(root_layer()->clip_tree_index());
      hud_layer()->SetScrollTreeIndex(root_layer()->scroll_tree_index());
      hud_layer()->set_property_tree_sequence_number(
          root_layer()->property_tree_sequence_number());
    }
  }

#if DCHECK_IS_ON()
  // Ensure property tree nodes were created for all layers. When using layer
  // lists, this can fail if blink doesn't setup layers or nodes correctly in
  // |PaintArtifactCompositor|. When not using layer lists, this can fail if
  // |PropertyTreeBuilder::BuildPropertyTrees| fails to create property tree
  // nodes.
  for (auto* layer : *this) {
    DCHECK(property_trees_.effect_tree.Node(layer->effect_tree_index()));
    DCHECK(property_trees_.transform_tree.Node(layer->transform_tree_index()));
    DCHECK(property_trees_.clip_tree.Node(layer->clip_tree_index()));
    DCHECK(property_trees_.scroll_tree.Node(layer->scroll_tree_index()));
  }
#else
  // This is a quick sanity check for readiness of paint properties.
  // TODO(crbug.com/913464): This is to help analysis of crashes of the bug.
  // Remove this CHECK when we close the bug.
  CHECK(property_trees_.effect_tree.Node(root_layer()->effect_tree_index()));
#endif

  draw_property_utils::UpdatePropertyTrees(this);

  LayerList update_layer_list;
  draw_property_utils::FindLayersThatNeedUpdates(this, &update_layer_list);
  bool did_paint_content = PaintContent(update_layer_list);
  return did_paint_content;
}

void LayerTreeHost::ApplyViewportChanges(
    const CompositorCommitData& commit_data) {
  gfx::Vector2dF inner_viewport_scroll_delta;
  if (commit_data.inner_viewport_scroll.element_id)
    inner_viewport_scroll_delta =
        commit_data.inner_viewport_scroll.scroll_delta;

  // When a new scroll-animation starts, it is necessary to check
  // |commit_data.manipulation_info| to make sure the scroll-animation was
  // started by an input event. If there is already an ongoing scroll-animation,
  // then it is necessary to only look at |commit_data.ongoing_scroll_animation|
  // (since it is possible for the scroll-animation to continue even if no event
  // was handled).
  bool new_ongoing_scroll = scroll_animation_.in_progress
                                ? commit_data.ongoing_scroll_animation
                                : (commit_data.ongoing_scroll_animation &&
                                   commit_data.manipulation_info);
  if (scroll_animation_.in_progress && !new_ongoing_scroll) {
    scroll_animation_.in_progress = false;
    if (!scroll_animation_.end_notification.is_null())
      std::move(scroll_animation_.end_notification).Run();
  } else {
    scroll_animation_.in_progress = new_ongoing_scroll;
  }

  if (inner_viewport_scroll_delta.IsZero() &&
      commit_data.page_scale_delta == 1.f &&
      commit_data.elastic_overscroll_delta.IsZero() &&
      !commit_data.top_controls_delta && !commit_data.bottom_controls_delta &&
      !commit_data.browser_controls_constraint_changed &&
      !commit_data.scroll_gesture_did_end &&
      commit_data.is_pinch_gesture_active ==
          is_pinch_gesture_active_from_impl_) {
    return;
  }
  is_pinch_gesture_active_from_impl_ = commit_data.is_pinch_gesture_active;

  if (auto* inner_scroll = property_trees()->scroll_tree.Node(
          pending_commit_state()->viewport_property_ids.inner_scroll)) {
    UpdateScrollOffsetFromImpl(
        inner_scroll->element_id, inner_viewport_scroll_delta,
        commit_data.inner_viewport_scroll.snap_target_element_ids);
  }

  ApplyPageScaleDeltaFromImplSide(commit_data.page_scale_delta);
  SetElasticOverscrollFromImplSide(pending_commit_state()->elastic_overscroll +
                                   commit_data.elastic_overscroll_delta);
  // TODO(ccameron): pass the elastic overscroll here so that input events
  // may be translated appropriately.
  client_->ApplyViewportChanges(
      {inner_viewport_scroll_delta, commit_data.elastic_overscroll_delta,
       commit_data.page_scale_delta, commit_data.is_pinch_gesture_active,
       commit_data.top_controls_delta, commit_data.bottom_controls_delta,
       commit_data.browser_controls_constraint,
       commit_data.scroll_gesture_did_end});
  SetNeedsUpdateLayers();
}

void LayerTreeHost::UpdateScrollOffsetFromImpl(
    const ElementId& id,
    const gfx::Vector2dF& delta,
    const absl::optional<TargetSnapAreaElementIds>& snap_target_ids) {
  if (IsUsingLayerLists()) {
    auto& scroll_tree = property_trees()->scroll_tree;
    auto new_offset = scroll_tree.current_scroll_offset(id) + delta;
    TRACE_EVENT_INSTANT2("cc", "NotifyDidScroll", TRACE_EVENT_SCOPE_THREAD,
                         "cur_y", scroll_tree.current_scroll_offset(id).y(),
                         "delta", delta.y());
    if (auto* scroll_node = scroll_tree.FindNodeFromElementId(id)) {
      // This update closely follows
      // blink::PropertyTreeManager::DirectlyUpdateScrollOffsetTransform.

      scroll_tree.SetScrollOffset(id, new_offset);
      // |blink::PropertyTreeManager::DirectlySetScrollOffset| (called from
      // |blink::PropertyTreeManager::DirectlyUpdateScrollOffsetTransform|)
      // marks the layer as needing to push properties in order to clobber
      // animations, but that is not needed for an impl-side scroll.

      // Update the offset in the transform node.
      DCHECK(scroll_node->transform_id != TransformTree::kInvalidNodeId);
      TransformTree& transform_tree = property_trees()->transform_tree;
      auto* transform_node = transform_tree.Node(scroll_node->transform_id);
      if (transform_node->scroll_offset != new_offset) {
        transform_node->scroll_offset = new_offset;
        transform_node->needs_local_transform_update = true;
        transform_node->transform_changed = true;
        transform_tree.set_needs_update(true);
      }

      // The transform tree has been modified which requires a call to
      // |LayerTreeHost::UpdateLayers| to update the property trees.
      SetNeedsUpdateLayers();
    }

    scroll_tree.NotifyDidCompositorScroll(id, new_offset, snap_target_ids);
  } else if (Layer* layer = LayerByElementId(id)) {
    layer->SetScrollOffsetFromImplSide(layer->scroll_offset() + delta);
    SetNeedsUpdateLayers();
  }
}

void LayerTreeHost::ApplyCompositorChanges(CompositorCommitData* commit_data) {
  DCHECK(commit_data);
  TRACE_EVENT0("cc", "LayerTreeHost::ApplyCompositorChanges");

  using perfetto::protos::pbzero::ChromeLatencyInfo;
  using perfetto::protos::pbzero::TrackEvent;

  for (auto& swap_promise : commit_data->swap_promises) {
    TRACE_EVENT(
        "input,benchmark", "LatencyInfo.Flow",
        [&swap_promise](perfetto::EventContext ctx) {
          ChromeLatencyInfo* info = ctx.event()->set_chrome_latency_info();
          info->set_trace_id(swap_promise->TraceId());
          info->set_step(ChromeLatencyInfo::STEP_MAIN_THREAD_SCROLL_UPDATE);
          tracing::FillFlowEvent(ctx, TrackEvent::LegacyEvent::FLOW_INOUT,
                                 swap_promise->TraceId());
        });
    swap_promise_manager_.QueueSwapPromise(std::move(swap_promise));
  }

  if (root_layer()) {
    auto& scroll_tree = property_trees()->scroll_tree;
    for (auto& scroll : commit_data->scrolls) {
      UpdateScrollOffsetFromImpl(scroll.element_id, scroll.scroll_delta,
                                 scroll.snap_target_element_ids);
    }
    for (auto& scrollbar : commit_data->scrollbars) {
      scroll_tree.NotifyDidChangeScrollbarsHidden(scrollbar.element_id,
                                                  scrollbar.hidden);
    }
  }

  client_->UpdateCompositorScrollState(*commit_data);

  // This needs to happen after scroll deltas have been sent to prevent top
  // controls from clamping the layout viewport both on the compositor and
  // on the main thread.
  ApplyViewportChanges(*commit_data);
}

void LayerTreeHost::ApplyMutatorEvents(std::unique_ptr<MutatorEvents> events) {
  DCHECK(task_runner_provider_->IsMainThread());
  if (!events->IsEmpty())
    mutator_host_->SetAnimationEvents(std::move(events));
}

void LayerTreeHost::RecordStartOfFrameMetrics() {
  client_->RecordStartOfFrameMetrics();
}

void LayerTreeHost::RecordEndOfFrameMetrics(
    base::TimeTicks frame_begin_time,
    ActiveFrameSequenceTrackers trackers) {
  client_->RecordEndOfFrameMetrics(frame_begin_time, trackers);
}

void LayerTreeHost::NotifyThroughputTrackerResults(
    CustomTrackerResults results) {
  client_->NotifyThroughputTrackerResults(std::move(results));
}

const base::WeakPtr<CompositorDelegateForInput>&
LayerTreeHost::GetDelegateForInput() const {
  return compositor_delegate_weak_ptr_;
}

void LayerTreeHost::UpdateBrowserControlsState(BrowserControlsState constraints,
                                               BrowserControlsState current,
                                               bool animate) {
  // Browser controls are only used in threaded mode but Blink layout tests may
  // call into this. The single threaded version is a no-op.
  proxy_->UpdateBrowserControlsState(constraints, current, animate);
}

void LayerTreeHost::AnimateLayers(base::TimeTicks monotonic_time) {
  std::unique_ptr<MutatorEvents> events = mutator_host_->CreateEvents();

  if (mutator_host_->TickAnimations(monotonic_time,
                                    property_trees()->scroll_tree, true))
    mutator_host_->UpdateAnimationState(true, events.get());

  if (!events->IsEmpty()) {
    // If not using layer lists, animation state changes will require
    // rebuilding property trees to track them.
    if (!IsUsingLayerLists())
      property_trees_.needs_rebuild = true;

    // A commit is required to push animation changes to the compositor.
    SetNeedsCommit();
  }
}

int LayerTreeHost::ScheduleMicroBenchmark(
    const std::string& benchmark_name,
    base::Value settings,
    MicroBenchmark::DoneCallback callback) {
  return micro_benchmark_controller_.ScheduleRun(
      benchmark_name, std::move(settings), std::move(callback));
}

bool LayerTreeHost::SendMessageToMicroBenchmark(int id, base::Value message) {
  return micro_benchmark_controller_.SendMessage(id, std::move(message));
}

void LayerTreeHost::SetLayerTreeMutator(
    std::unique_ptr<LayerTreeMutator> mutator) {
  // The animation worklet system assumes that the mutator will never be called
  // from the main thread, which will not be the case if we're running in
  // single-threaded mode.
  if (!task_runner_provider_->HasImplThread()) {
    DLOG(ERROR) << "LayerTreeMutator not supported in single-thread mode";
    return;
  }
  proxy_->SetMutator(std::move(mutator));
}

void LayerTreeHost::SetPaintWorkletLayerPainter(
    std::unique_ptr<PaintWorkletLayerPainter> painter) {
  // The paint worklet system assumes that the painter will never be called from
  // the main thread, which will not be the case if we're running in
  // single-threaded mode.
  DCHECK(task_runner_provider_->HasImplThread())
      << "PaintWorkletLayerPainter not supported in single-thread mode";
  proxy_->SetPaintWorkletLayerPainter(std::move(painter));
}

bool LayerTreeHost::IsSingleThreaded() const {
  DCHECK(compositor_mode_ != CompositorMode::SINGLE_THREADED ||
         !task_runner_provider_->HasImplThread());
  return compositor_mode_ == CompositorMode::SINGLE_THREADED;
}

bool LayerTreeHost::IsThreaded() const {
  DCHECK(compositor_mode_ != CompositorMode::THREADED ||
         task_runner_provider_->HasImplThread());
  return compositor_mode_ == CompositorMode::THREADED;
}

void LayerTreeHost::RequestPresentationTimeForNextFrame(
    PresentationTimeCallbackBuffer::MainCallback callback) {
  pending_commit_state()->pending_presentation_time_callbacks.push_back(
      std::move(callback));
}

void LayerTreeHost::RequestScrollAnimationEndNotification(
    base::OnceClosure callback) {
  DCHECK(scroll_animation_.end_notification.is_null());
  if (scroll_animation_.in_progress)
    scroll_animation_.end_notification = std::move(callback);
  else
    std::move(callback).Run();
}

void LayerTreeHost::SetRootLayer(scoped_refptr<Layer> new_root_layer) {
  if (root_layer() == new_root_layer.get())
    return;

  if (root_layer()) {
    WaitForCommitCompletion();
    root_layer()->SetLayerTreeHost(nullptr);
  }
  pending_commit_state()->root_layer = new_root_layer;
  if (root_layer()) {
    DCHECK(!root_layer()->parent());
    root_layer()->SetLayerTreeHost(this);
  }

  if (hud_layer()) {
    WaitForCommitCompletion();
    hud_layer()->RemoveFromParent();
  }

  // Reset gpu rasterization tracking.
  // This flag is sticky until a new tree comes along.
  pending_commit_state()->needs_gpu_rasterization_histogram = IsThreaded();

  SetNeedsFullTreeSync();
}

void LayerTreeHost::RegisterViewportPropertyIds(
    const ViewportPropertyIds& ids) {
  DCHECK(IsUsingLayerLists());
  pending_commit_state()->viewport_property_ids = ids;
  // Outer viewport properties exist only if inner viewport property exists.
  DCHECK(ids.inner_scroll != ScrollTree::kInvalidNodeId ||
         (ids.outer_scroll == ScrollTree::kInvalidNodeId &&
          ids.outer_clip == ClipTree::kInvalidNodeId));
}

Layer* LayerTreeHost::InnerViewportScrollLayerForTesting() {
  auto* scroll_node = property_trees()->scroll_tree.Node(
      pending_commit_state()->viewport_property_ids.inner_scroll);
  return scroll_node ? LayerByElementId(scroll_node->element_id) : nullptr;
}

Layer* LayerTreeHost::OuterViewportScrollLayerForTesting() {
  return LayerByElementId(OuterViewportScrollElementId());
}

ElementId LayerTreeHost::OuterViewportScrollElementId() const {
  auto* scroll_node = property_trees()->scroll_tree.Node(
      pending_commit_state()->viewport_property_ids.outer_scroll);
  return scroll_node ? scroll_node->element_id : ElementId();
}

void LayerTreeHost::RegisterSelection(const LayerSelection& selection) {
  if (pending_commit_state()->selection == selection)
    return;

  pending_commit_state()->selection = selection;
  SetNeedsCommit();
}

void LayerTreeHost::SetHaveScrollEventHandlers(bool have_event_handlers) {
  if (pending_commit_state()->have_scroll_event_handlers == have_event_handlers)
    return;

  pending_commit_state()->have_scroll_event_handlers = have_event_handlers;
  SetNeedsCommit();
}

void LayerTreeHost::SetEventListenerProperties(
    EventListenerClass event_class,
    EventListenerProperties properties) {
  if (event_listener_properties(event_class) == properties)
    return;
  const size_t index = static_cast<size_t>(event_class);
  pending_commit_state()->event_listener_properties[index] = properties;
  SetNeedsCommit();
}

void LayerTreeHost::SetViewportRectAndScale(
    const gfx::Rect& device_viewport_rect,
    float device_scale_factor,
    const viz::LocalSurfaceId& local_surface_id_from_parent) {
  const viz::LocalSurfaceId previous_local_surface_id =
      pending_commit_state()->local_surface_id_from_parent;
  SetLocalSurfaceIdFromParent(local_surface_id_from_parent);

  TRACE_EVENT_NESTABLE_ASYNC_END1("cc", "LayerTreeHostSize",
                                  TRACE_ID_LOCAL(this), "id", id_);
  TRACE_EVENT_NESTABLE_ASYNC_BEGIN2("cc", "LayerTreeHostSize",
                                    TRACE_ID_LOCAL(this), "size",
                                    device_viewport_rect.ToString(), "lsid",
                                    local_surface_id_from_parent.ToString());

  bool device_viewport_rect_changed = false;
  if (pending_commit_state()->device_viewport_rect != device_viewport_rect) {
    pending_commit_state()->device_viewport_rect = device_viewport_rect;
    device_viewport_rect_changed = true;
  }
  bool painted_device_scale_factor_changed = false;
  bool device_scale_factor_changed = false;
  if (settings_.use_painted_device_scale_factor) {
    DCHECK_EQ(pending_commit_state()->device_scale_factor, 1.f);
    if (pending_commit_state()->painted_device_scale_factor !=
        device_scale_factor) {
      pending_commit_state()->painted_device_scale_factor = device_scale_factor;
      painted_device_scale_factor_changed = true;
    }
  } else {
    DCHECK_EQ(pending_commit_state()->painted_device_scale_factor, 1.f);
    if (pending_commit_state()->device_scale_factor != device_scale_factor) {
      pending_commit_state()->device_scale_factor = device_scale_factor;
      device_scale_factor_changed = true;
    }
  }

  // If a new viz::LocalSurfaceId has been provided, and the viewport has
  // changed, we need not begin new frames until it has activated.
  if (previous_local_surface_id != local_surface_id_from_parent &&
      device_viewport_rect_changed && features::IsSurfaceSyncThrottling()) {
    SetTargetLocalSurfaceId(local_surface_id_from_parent);
  }

  if (device_viewport_rect_changed || painted_device_scale_factor_changed ||
      device_scale_factor_changed) {
    SetPropertyTreesNeedRebuild();
    SetNeedsCommit();
  }
}

void LayerTreeHost::SetVisualDeviceViewportIntersectionRect(
    const gfx::Rect& intersection_rect) {
  if (intersection_rect == visual_device_viewport_intersection_rect_)
    return;

  visual_device_viewport_intersection_rect_ = intersection_rect;
}

void LayerTreeHost::SetVisualDeviceViewportSize(
    const gfx::Size& visual_device_viewport_size) {
  if (visual_device_viewport_size ==
      pending_commit_state()->visual_device_viewport_size)
    return;

  pending_commit_state()->visual_device_viewport_size =
      visual_device_viewport_size;
  SetNeedsCommit();
}

void LayerTreeHost::SetBrowserControlsParams(
    const BrowserControlsParams& params) {
  if (pending_commit_state()->browser_controls_params == params)
    return;

  pending_commit_state()->browser_controls_params = params;
  SetNeedsCommit();
}

void LayerTreeHost::SetBrowserControlsShownRatio(float top_ratio,
                                                 float bottom_ratio) {
  if (pending_commit_state()->top_controls_shown_ratio == top_ratio &&
      pending_commit_state()->bottom_controls_shown_ratio == bottom_ratio)
    return;

  pending_commit_state()->top_controls_shown_ratio = top_ratio;
  pending_commit_state()->bottom_controls_shown_ratio = bottom_ratio;
  SetNeedsCommit();
}

void LayerTreeHost::SetOverscrollBehavior(const OverscrollBehavior& behavior) {
  if (pending_commit_state()->overscroll_behavior == behavior)
    return;
  pending_commit_state()->overscroll_behavior = behavior;
  SetNeedsCommit();
}

void LayerTreeHost::SetPageScaleFactorAndLimits(float page_scale_factor,
                                                float min_page_scale_factor,
                                                float max_page_scale_factor) {
  if (pending_commit_state()->page_scale_factor == page_scale_factor &&
      pending_commit_state()->min_page_scale_factor == min_page_scale_factor &&
      pending_commit_state()->max_page_scale_factor == max_page_scale_factor)
    return;
  DCHECK_GE(page_scale_factor, min_page_scale_factor);
  DCHECK_LE(page_scale_factor, max_page_scale_factor);
  // We should never process non-unit page_scale_delta for an OOPIF subframe.
  // TODO(wjmaclean): Remove this dcheck as a pre-condition to closing the bug.
  // https://crbug.com/845097
  DCHECK(!settings_.is_layer_tree_for_subframe ||
         page_scale_factor == pending_commit_state()->page_scale_factor)
      << "Setting PSF in oopif subframe: old psf = "
      << pending_commit_state()->page_scale_factor
      << ", new psf = " << page_scale_factor;

  pending_commit_state()->page_scale_factor = page_scale_factor;
  pending_commit_state()->min_page_scale_factor = min_page_scale_factor;
  pending_commit_state()->max_page_scale_factor = max_page_scale_factor;
  SetPropertyTreesNeedRebuild();
  SetNeedsCommit();
}

void LayerTreeHost::StartPageScaleAnimation(const gfx::Point& target_offset,
                                            bool use_anchor,
                                            float scale,
                                            base::TimeDelta duration) {
  pending_commit_state()->pending_page_scale_animation =
      std::make_unique<PendingPageScaleAnimation>(target_offset, use_anchor,
                                                  scale, duration);

  SetNeedsCommit();
}

bool LayerTreeHost::HasPendingPageScaleAnimation() const {
  return !!pending_commit_state()->pending_page_scale_animation.get();
}

void LayerTreeHost::SetRecordingScaleFactor(float recording_scale_factor) {
  if (recording_scale_factor_ == recording_scale_factor)
    return;
  recording_scale_factor_ = recording_scale_factor;
}

void LayerTreeHost::SetDisplayColorSpaces(
    const gfx::DisplayColorSpaces& display_color_spaces) {
  if (pending_commit_state()->display_color_spaces == display_color_spaces)
    return;
  pending_commit_state()->display_color_spaces = display_color_spaces;
  for (auto* layer : *this)
    layer->SetNeedsDisplay();
}

void LayerTreeHost::UpdateViewportIsMobileOptimized(
    bool is_viewport_mobile_optimized) {
  if (pending_commit_state()->is_viewport_mobile_optimized ==
      is_viewport_mobile_optimized)
    return;
  pending_commit_state()->is_viewport_mobile_optimized =
      is_viewport_mobile_optimized;
  SetNeedsCommit();
}

void LayerTreeHost::SetPrefersReducedMotion(bool prefers_reduced_motion) {
  if (pending_commit_state()->prefers_reduced_motion == prefers_reduced_motion)
    return;
  pending_commit_state()->prefers_reduced_motion = prefers_reduced_motion;
  SetNeedsCommit();
}

void LayerTreeHost::SetMayThrottleIfUndrawnFrames(
    bool may_throttle_if_undrawn_frames) {
  if (pending_commit_state()->may_throttle_if_undrawn_frames ==
      may_throttle_if_undrawn_frames)
    return;
  pending_commit_state()->may_throttle_if_undrawn_frames =
      may_throttle_if_undrawn_frames;
  SetNeedsCommit();
}

bool LayerTreeHost::GetMayThrottleIfUndrawnFramesForTesting() const {
  return pending_commit_state()->may_throttle_if_undrawn_frames;
}

void LayerTreeHost::SetExternalPageScaleFactor(
    float page_scale_factor,
    bool is_external_pinch_gesture_active) {
  if (pending_commit_state()->external_page_scale_factor == page_scale_factor &&
      pending_commit_state()->is_external_pinch_gesture_active ==
          is_external_pinch_gesture_active) {
    return;
  }

  pending_commit_state()->external_page_scale_factor = page_scale_factor;
  pending_commit_state()->is_external_pinch_gesture_active =
      is_external_pinch_gesture_active;
  SetNeedsCommit();
}

void LayerTreeHost::SetLocalSurfaceIdFromParent(
    const viz::LocalSurfaceId& local_surface_id_from_parent) {
  // If the viz::LocalSurfaceId is invalid we will be hitting the early exit.
  // However creating a hash for tracing of an invalid id throw an error. So
  // exit here. This is either from unit testing where no ids are being setup,
  // or from a disconnect in Renderer and Browser startup, in which Renderers
  // have a partial state before the Browser sends the full visual properties.
  //
  // TODO(jonross): Untangle startup so that we don't have this invalid partial
  // state. (https://crbug.com/1185286) (https://crbug.com/419087)
  if (pending_commit_state()->local_surface_id_from_parent ==
      local_surface_id_from_parent)
    return;
  const viz::LocalSurfaceId current_local_surface_id_from_parent =
      pending_commit_state()->local_surface_id_from_parent;

  // These traces are split into two due to the usage of TRACE_ID_GLOBAL for the
  // incoming flow (it comes from a different process), and TRACE_ID_LOCAL for
  // the outgoing flow. The outgoing flow uses local to ensure that it doesn't
  // flow into the wrong trace in different process.
  TRACE_EVENT_WITH_FLOW2(
      TRACE_DISABLED_BY_DEFAULT("viz.surface_id_flow"),
      "LocalSurfaceId.Submission.Flow",
      TRACE_ID_GLOBAL(local_surface_id_from_parent.submission_trace_id()),
      TRACE_EVENT_FLAG_FLOW_IN, "step", "SetLocalSurfaceIdFromParent",
      "local_surface_id", local_surface_id_from_parent.ToString());
  TRACE_EVENT_WITH_FLOW2(
      TRACE_DISABLED_BY_DEFAULT("viz.surface_id_flow"),
      "LocalSurfaceId.Submission.Flow",
      TRACE_ID_LOCAL(local_surface_id_from_parent.submission_trace_id()),
      TRACE_EVENT_FLAG_FLOW_OUT, "step", "SetLocalSurfaceIdFromParent",
      "local_surface_id", local_surface_id_from_parent.ToString());
  // Always update the cached state of the viz::LocalSurfaceId to reflect the
  // latest value received from our parent.
  pending_commit_state()->local_surface_id_from_parent =
      local_surface_id_from_parent;

  // If the parent sequence number has not advanced, then there is no need to
  // commit anything. This can occur when the child sequence number has
  // advanced. Which means that child has changed visual properites, and the
  // parent agreed upon these without needing to further advance its sequence
  // number. When this occurs the child is already up-to-date and a commit here
  // is simply redundant.
  if (AreEmbedTokensEqual(current_local_surface_id_from_parent,
                          local_surface_id_from_parent) &&
      AreParentSequencesEqual(current_local_surface_id_from_parent,
                              local_surface_id_from_parent)) {
    return;
  }
  UpdateDeferMainFrameUpdateInternal();
  SetNeedsCommit();
}

void LayerTreeHost::RequestNewLocalSurfaceId() {
  // We can still request a new viz::LocalSurfaceId but that request will be
  // deferred until we have a valid viz::LocalSurfaceId from the parent.
  if (pending_commit_state()->new_local_surface_id_request)
    return;
  pending_commit_state()->new_local_surface_id_request = true;
  SetNeedsCommit();
}

void LayerTreeHost::SetVisualPropertiesUpdateDuration(
    base::TimeDelta visual_properties_update_duration) {
  pending_commit_state()->visual_properties_update_duration =
      visual_properties_update_duration;
}

void LayerTreeHost::RegisterLayer(Layer* layer) {
  DCHECK(!LayerById(layer->id()));
  DCHECK(!in_paint_layer_contents_);
  layer_id_map_[layer->id()] = layer;
  if (!IsUsingLayerLists() && layer->element_id()) {
    mutator_host_->RegisterElementId(layer->element_id(),
                                     ElementListType::ACTIVE);
  }
}

void LayerTreeHost::UnregisterLayer(Layer* layer) {
  DCHECK(LayerById(layer->id()));
  DCHECK(!in_paint_layer_contents_);
  if (!IsUsingLayerLists() && layer->element_id()) {
    mutator_host_->UnregisterElementId(layer->element_id(),
                                       ElementListType::ACTIVE);
  }
  pending_commit_state()->layers_that_should_push_properties.erase(layer);
  layer_id_map_.erase(layer->id());
}

Layer* LayerTreeHost::LayerById(int id) {
  auto iter = layer_id_map_.find(id);
  return iter != layer_id_map_.end() ? iter->second : nullptr;
}

bool LayerTreeHost::PaintContent(const LayerList& update_layer_list) {
  base::AutoReset<bool> painting(&in_paint_layer_contents_, true);
  bool did_paint_content = false;
  for (const auto& layer : update_layer_list) {
    did_paint_content |= layer->Update();
  }
  return did_paint_content;
}

void LayerTreeHost::AddSurfaceRange(const viz::SurfaceRange& surface_range) {
  if (++pending_commit_state()->surface_ranges[surface_range] == 1)
    pending_commit_state()->needs_surface_ranges_sync = true;
}

void LayerTreeHost::RemoveSurfaceRange(const viz::SurfaceRange& surface_range) {
  auto iter = pending_commit_state()->surface_ranges.find(surface_range);
  if (iter == pending_commit_state()->surface_ranges.end())
    return;

  if (--iter->second <= 0) {
    pending_commit_state()->surface_ranges.erase(iter);
    pending_commit_state()->needs_surface_ranges_sync = true;
  }
}

void LayerTreeHost::AddLayerShouldPushProperties(Layer* layer) {
  pending_commit_state()->layers_that_should_push_properties.insert(layer);
}

void LayerTreeHost::SetPageScaleFromImplSide(float page_scale) {
  DCHECK(CommitRequested());
  // We should never process non-unit page_scale_delta for an OOPIF subframe.
  // TODO(wjmaclean): Remove this check as a pre-condition to closing the bug.
  // https://crbug.com/845097
  DCHECK(!settings_.is_layer_tree_for_subframe ||
         page_scale == pending_commit_state()->page_scale_factor)
      << "Setting PSF in oopif subframe: old psf = "
      << pending_commit_state()->page_scale_factor
      << ", new psf = " << page_scale;
  pending_commit_state()->page_scale_factor = page_scale;
  SetPropertyTreesNeedRebuild();
}

void LayerTreeHost::SetElasticOverscrollFromImplSide(
    gfx::Vector2dF elastic_overscroll) {
  DCHECK(CommitRequested());
  pending_commit_state()->elastic_overscroll = elastic_overscroll;
}

void LayerTreeHost::UpdateHudLayer(bool show_hud_info) {
  if (show_hud_info) {
    if (!hud_layer()) {
      hud_layer_ = HeadsUpDisplayLayer::Create();
      pending_commit_state()->hud_layer_id = hud_layer()->id();
    }
    if (root_layer() && !hud_layer()->parent())
      root_layer()->AddChild(hud_layer());
    hud_layer()->UpdateLocationAndSize(
        pending_commit_state()->device_viewport_rect.size(),
        pending_commit_state()->device_scale_factor);
    if (pending_commit_state()->debug_state.show_web_vital_metrics) {
      // This WebVitalMetrics is filled by the main frame, which is equivalent
      // to WebPerf's numbers. The main frame's number doesn't include any
      // iframes. UMA/UKM records metrics for the entire page aggregating all
      // the frames. The page metrics are in the browser process.
      // TODO(weiliangc): Get the page metrics for display.
      auto metrics = client_->GetWebVitalMetrics();
      if (metrics && metrics->HasValue())
        hud_layer()->UpdateWebVitalMetrics(std::move(metrics));
    }
  } else if (hud_layer()) {
    hud_layer()->RemoveFromParent();
    hud_layer_ = nullptr;
    pending_commit_state()->hud_layer_id = Layer::INVALID_ID;
  }
}

bool LayerTreeHost::is_hud_layer(const Layer* layer) const {
  return hud_layer() == layer;
}

void LayerTreeHost::SetNeedsFullTreeSync() {
  pending_commit_state()->needs_full_tree_sync = true;
  property_trees_.needs_rebuild = true;
  SetNeedsCommit();
}

void LayerTreeHost::ResetNeedsFullTreeSyncForTesting() {
  pending_commit_state()->needs_full_tree_sync = false;
}

void LayerTreeHost::SetPropertyTreesNeedRebuild() {
  property_trees_.needs_rebuild = true;
  SetNeedsUpdateLayers();
}

void LayerTreeHost::PushLayerTreePropertiesTo(CommitState* state,
                                              LayerTreeImpl* tree_impl) {
  DCHECK(state);
  tree_impl->set_needs_full_tree_sync(state->needs_full_tree_sync);

  if (state->hud_layer_id != Layer::INVALID_ID) {
    LayerImpl* hud_impl = tree_impl->LayerById(state->hud_layer_id);
    tree_impl->set_hud_layer(static_cast<HeadsUpDisplayLayerImpl*>(hud_impl));
  } else {
    tree_impl->set_hud_layer(nullptr);
  }

  tree_impl->set_background_color(state->background_color);
  tree_impl->set_have_scroll_event_handlers(state->have_scroll_event_handlers);
  tree_impl->set_event_listener_properties(
      EventListenerClass::kTouchStartOrMove,
      state->GetEventListenerProperties(EventListenerClass::kTouchStartOrMove));
  tree_impl->set_event_listener_properties(
      EventListenerClass::kMouseWheel,
      state->GetEventListenerProperties(EventListenerClass::kMouseWheel));
  tree_impl->set_event_listener_properties(
      EventListenerClass::kTouchEndOrCancel,
      state->GetEventListenerProperties(EventListenerClass::kTouchEndOrCancel));

  tree_impl->SetViewportPropertyIds(state->viewport_property_ids);

  tree_impl->RegisterSelection(state->selection);

  tree_impl->PushPageScaleFromMainThread(state->page_scale_factor,
                                         state->min_page_scale_factor,
                                         state->max_page_scale_factor);

  tree_impl->SetBrowserControlsParams(state->browser_controls_params);
  tree_impl->set_overscroll_behavior(state->overscroll_behavior);
  tree_impl->PushBrowserControlsFromMainThread(
      state->top_controls_shown_ratio, state->bottom_controls_shown_ratio);
  tree_impl->elastic_overscroll()->PushMainToPending(state->elastic_overscroll);
  if (tree_impl->IsActiveTree())
    tree_impl->elastic_overscroll()->PushPendingToActive();

  tree_impl->SetDisplayColorSpaces(state->display_color_spaces);
  tree_impl->SetExternalPageScaleFactor(state->external_page_scale_factor);

  tree_impl->set_painted_device_scale_factor(
      state->painted_device_scale_factor);
  tree_impl->SetDeviceScaleFactor(state->device_scale_factor);
  tree_impl->SetDeviceViewportRect(state->device_viewport_rect);

  if (state->new_local_surface_id_request)
    tree_impl->RequestNewLocalSurfaceId();

  tree_impl->SetLocalSurfaceIdFromParent(state->local_surface_id_from_parent);
  tree_impl->SetVisualPropertiesUpdateDuration(
      state->visual_properties_update_duration);

  if (state->pending_page_scale_animation) {
    tree_impl->SetPendingPageScaleAnimation(
        std::move(state->pending_page_scale_animation));
  }

  if (state->force_send_metadata_request)
    tree_impl->RequestForceSendMetadata();

  tree_impl->set_has_ever_been_drawn(false);

  // TODO(ericrk): The viewport changes caused by |top_controls_shown_ratio_|
  // changes should propagate back to the main tree. This does not currently
  // happen, so we must force the impl tree to update its viewports if
  // |top_controls_shown_ratio_| is greater than 0.0f and less than 1.0f
  // (partially shown). crbug.com/875943
  if (state->top_controls_shown_ratio > 0.0f &&
      state->top_controls_shown_ratio < 1.0f) {
    tree_impl->UpdateViewportContainerSizes();
  }

  tree_impl->set_display_transform_hint(state->display_transform_hint);

  if (state->delegated_ink_metadata)
    tree_impl->set_delegated_ink_metadata(
        std::move(state->delegated_ink_metadata));

  // Transfer page transition directives.
  for (auto& request : state->document_transition_requests)
    tree_impl->AddDocumentTransitionRequest(std::move(request));
}

void LayerTreeHost::PushLayerTreeHostPropertiesTo(
    LayerTreeHostImpl* host_impl) {
  CommitState* state = active_commit_state();
  DCHECK(state);
  // TODO(bokan): The |external_pinch_gesture_active| should not be going
  // through the LayerTreeHost but directly from InputHandler to InputHandler.
  host_impl->SetExternalPinchGestureActive(
      state->is_external_pinch_gesture_active);

  RecordGpuRasterizationHistogram(host_impl);

  host_impl->SetDebugState(state->debug_state);
  host_impl->SetVisualDeviceViewportSize(state->visual_device_viewport_size);
  host_impl->set_viewport_mobile_optimized(state->is_viewport_mobile_optimized);
  host_impl->SetPrefersReducedMotion(state->prefers_reduced_motion);
  host_impl->SetMayThrottleIfUndrawnFrames(
      state->may_throttle_if_undrawn_frames);
}

Layer* LayerTreeHost::LayerByElementId(ElementId element_id) {
  auto iter = element_layers_map_.find(element_id);
  return iter != element_layers_map_.end() ? iter->second : nullptr;
}

const Layer* LayerTreeHost::LayerByElementId(ElementId element_id) const {
  auto iter = element_layers_map_.find(element_id);
  return iter != element_layers_map_.end() ? iter->second : nullptr;
}

void LayerTreeHost::RegisterElement(ElementId element_id,
                                    Layer* layer) {
  element_layers_map_[element_id] = layer;
  if (!IsUsingLayerLists())
    mutator_host_->RegisterElementId(element_id, ElementListType::ACTIVE);
}

void LayerTreeHost::UnregisterElement(ElementId element_id) {
  if (!IsUsingLayerLists())
    mutator_host_->UnregisterElementId(element_id, ElementListType::ACTIVE);
  element_layers_map_.erase(element_id);
}

void LayerTreeHost::UpdateActiveElements() {
  DCHECK(IsUsingLayerLists());
  mutator_host_->UpdateRegisteredElementIds(ElementListType::ACTIVE);
}

void LayerTreeHost::SetElementIdsForTesting() {
  for (auto* layer : *this)
    layer->SetElementId(LayerIdToElementIdForTesting(layer->id()));
}

void LayerTreeHost::BuildPropertyTreesForTesting() {
  PropertyTreeBuilder::BuildPropertyTrees(this);
}

bool LayerTreeHost::IsElementInPropertyTrees(ElementId element_id,
                                             ElementListType list_type) const {
  if (IsUsingLayerLists()) {
    return list_type == ElementListType::ACTIVE &&
           property_trees()->HasElement(element_id);
  }
  return list_type == ElementListType::ACTIVE && LayerByElementId(element_id);
}

void LayerTreeHost::SetMutatorsNeedCommit() {
  SetNeedsCommit();
}

void LayerTreeHost::SetMutatorsNeedRebuildPropertyTrees() {
  property_trees_.needs_rebuild = true;
}

void LayerTreeHost::SetElementFilterMutated(ElementId element_id,
                                            ElementListType list_type,
                                            const FilterOperations& filters) {
  if (IsUsingLayerLists()) {
    // In BlinkGenPropertyTrees/CompositeAfterPaint we always have property
    // tree nodes and can set the filter directly on the effect node.
    property_trees_.effect_tree.OnFilterAnimated(element_id, filters);
    return;
  }

  Layer* layer = LayerByElementId(element_id);
  DCHECK(layer);
  layer->OnFilterAnimated(filters);
}

void LayerTreeHost::SetElementBackdropFilterMutated(
    ElementId element_id,
    ElementListType list_type,
    const FilterOperations& backdrop_filters) {
  if (IsUsingLayerLists()) {
    // In BlinkGenPropertyTrees/CompositeAfterPaint we always have property
    // tree nodes and can set the backdrop_filter directly on the effect node.
    property_trees_.effect_tree.OnBackdropFilterAnimated(element_id,
                                                         backdrop_filters);
    return;
  }

  Layer* layer = LayerByElementId(element_id);
  DCHECK(layer);
  layer->OnBackdropFilterAnimated(backdrop_filters);
}

void LayerTreeHost::SetElementOpacityMutated(ElementId element_id,
                                             ElementListType list_type,
                                             float opacity) {
  DCHECK_GE(opacity, 0.f);
  DCHECK_LE(opacity, 1.f);

  if (IsUsingLayerLists()) {
    property_trees_.effect_tree.OnOpacityAnimated(element_id, opacity);
    return;
  }

  Layer* layer = LayerByElementId(element_id);
  DCHECK(layer);
  layer->OnOpacityAnimated(opacity);

  if (EffectNode* node =
          property_trees_.effect_tree.Node(layer->effect_tree_index())) {
    DCHECK_EQ(layer->effect_tree_index(), node->id);
    if (node->opacity == opacity)
      return;

    node->opacity = opacity;
    property_trees_.effect_tree.set_needs_update(true);
  }

  SetNeedsUpdateLayers();
}

void LayerTreeHost::SetElementTransformMutated(
    ElementId element_id,
    ElementListType list_type,
    const gfx::Transform& transform) {
  if (IsUsingLayerLists()) {
    property_trees_.transform_tree.OnTransformAnimated(element_id, transform);
    return;
  }

  Layer* layer = LayerByElementId(element_id);
  DCHECK(layer);
  layer->OnTransformAnimated(transform);

  if (layer->has_transform_node()) {
    TransformNode* node =
        property_trees_.transform_tree.Node(layer->transform_tree_index());
    if (node->local == transform)
      return;

    node->local = transform;
    node->needs_local_transform_update = true;
    node->has_potential_animation = true;
    property_trees_.transform_tree.set_needs_update(true);
  }

  SetNeedsUpdateLayers();
}

void LayerTreeHost::SetElementScrollOffsetMutated(
    ElementId element_id,
    ElementListType list_type,
    const gfx::PointF& scroll_offset) {
  // Do nothing. Scroll deltas will be sent from the compositor thread back
  // to the main thread in the same manner as during non-animated
  // compositor-driven scrolling.
}

void LayerTreeHost::ElementIsAnimatingChanged(
    const PropertyToElementIdMap& element_id_map,
    ElementListType list_type,
    const PropertyAnimationState& mask,
    const PropertyAnimationState& state) {
  DCHECK_EQ(ElementListType::ACTIVE, list_type);
  property_trees()->ElementIsAnimatingChanged(element_id_map, mask, state,
                                              true);
}

void LayerTreeHost::MaximumScaleChanged(ElementId element_id,
                                        ElementListType list_type,
                                        float maximum_scale) {
  DCHECK_EQ(ElementListType::ACTIVE, list_type);
  property_trees()->MaximumAnimationScaleChanged(element_id, maximum_scale);
}

gfx::PointF LayerTreeHost::GetScrollOffsetForAnimation(
    ElementId element_id) const {
  return property_trees()->scroll_tree.current_scroll_offset(element_id);
}

void LayerTreeHost::QueueImageDecode(const PaintImage& image,
                                     base::OnceCallback<void(bool)> callback) {
  TRACE_EVENT0("cc", "LayerTreeHost::QueueImageDecode");
  int next_id = s_image_decode_sequence_number.GetNext();
  pending_commit_state()->queued_image_decodes.emplace_back(
      next_id, std::make_unique<PaintImage>(image));
  pending_image_decodes_.emplace(next_id, std::move(callback));
  SetNeedsCommit();
}

LayerListIterator LayerTreeHost::begin() {
  return LayerListIterator(root_layer());
}

LayerListConstIterator LayerTreeHost::begin() const {
  return LayerListConstIterator(root_layer());
}

LayerListIterator LayerTreeHost::end() {
  return LayerListIterator(nullptr);
}

LayerListConstIterator LayerTreeHost::end() const {
  return LayerListConstIterator(nullptr);
}

LayerListReverseIterator LayerTreeHost::rbegin() {
  return LayerListReverseIterator(root_layer());
}

LayerListReverseConstIterator LayerTreeHost::rbegin() const {
  return LayerListReverseConstIterator(root_layer());
}

LayerListReverseIterator LayerTreeHost::rend() {
  return LayerListReverseIterator(nullptr);
}

LayerListReverseConstIterator LayerTreeHost::rend() const {
  return LayerListReverseConstIterator(nullptr);
}

void LayerTreeHost::SetPropertyTreesForTesting(
    const PropertyTrees* property_trees) {
  property_trees_ = *property_trees;
}

void LayerTreeHost::SetNeedsDisplayOnAllLayers() {
  for (auto* layer : *this)
    layer->SetNeedsDisplay();
}

void LayerTreeHost::SetHasCopyRequest(bool has_copy_request) {
  has_copy_request_ = has_copy_request;
}

void LayerTreeHost::RequestBeginMainFrameNotExpected(bool new_state) {
  proxy_->RequestBeginMainFrameNotExpected(new_state);
}

void LayerTreeHost::SetSourceURL(ukm::SourceId source_id, const GURL& url) {
  // Clears image caches and resets the scheduling history for the content
  // produced by this host so far.
  pending_commit_state()->clear_caches_on_next_commit = true;
  proxy_->SetSourceURL(source_id, url);
  // If this is not used as a common web page, don't show HUD.
  if (!url.SchemeIsHTTPOrHTTPS())
    pending_commit_state()->debug_state.TurnOffHudInfoDisplay();
}

base::ReadOnlySharedMemoryRegion
LayerTreeHost::CreateSharedMemoryForSmoothnessUkm() {
  const auto size = sizeof(UkmSmoothnessDataShared);
  auto ukm_smoothness_mapping = base::ReadOnlySharedMemoryRegion::Create(size);
  if (!ukm_smoothness_mapping.IsValid())
    return {};
  proxy_->SetUkmSmoothnessDestination(
      std::move(ukm_smoothness_mapping.mapping));
  return std::move(ukm_smoothness_mapping.region);
}

void LayerTreeHost::SetRenderFrameObserver(
    std::unique_ptr<RenderFrameMetadataObserver> observer) {
  proxy_->SetRenderFrameObserver(std::move(observer));
}

void LayerTreeHost::SetEnableFrameRateThrottling(
    bool enable_frame_rate_throttling) {
  proxy_->SetEnableFrameRateThrottling(enable_frame_rate_throttling);
}

void LayerTreeHost::SetDelegatedInkMetadata(
    std::unique_ptr<gfx::DelegatedInkMetadata> metadata) {
  pending_commit_state()->delegated_ink_metadata = std::move(metadata);
  SetNeedsCommit();
}

gfx::RenderingPipeline* LayerTreeHost::TakeMainPipeline() {
  auto* pipeline = main_thread_pipeline_;
  main_thread_pipeline_ = nullptr;
  return pipeline;
}

gfx::RenderingPipeline* LayerTreeHost::TakeCompositorPipeline() {
  auto* pipeline = compositor_thread_pipeline_;
  compositor_thread_pipeline_ = nullptr;
  return pipeline;
}

std::vector<base::OnceClosure>
LayerTreeHost::TakeDocumentTransitionCallbacksForTesting() {
  std::vector<base::OnceClosure> result;
  for (auto& item : document_transition_callbacks_)
    result.push_back(std::move(item.second));
  document_transition_callbacks_.clear();
  return result;
}

uint32_t LayerTreeHost::GetAverageThroughput() const {
  return proxy_->GetAverageThroughput();
}

}  // namespace cc