(Reland) Discard compositor frames from unloaded web content

cc/trees/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>
@@ skipping 86 matching lines @@
     : micro_benchmark_controller_(this),
       image_worker_task_runner_(params->image_worker_task_runner),
       compositor_mode_(mode),
       ui_resource_manager_(base::MakeUnique<UIResourceManager>()),
       client_(params->client),
       rendering_stats_instrumentation_(RenderingStatsInstrumentation::Create()),
       settings_(*params->settings),
       debug_state_(settings_.initial_debug_state),
       id_(s_layer_tree_host_sequence_number.GetNext() + 1),
       task_graph_runner_(params->task_graph_runner),
+      content_source_id_(0),
       event_listener_properties_(),
       mutator_host_(params->mutator_host) {
   DCHECK(task_graph_runner_);
   DCHECK(!settings_.enable_checker_imaging || image_worker_task_runner_);
   DCHECK(!settings_.enable_checker_imaging ||
          settings_.image_decode_tasks_enabled);
 
   mutator_host_->SetMutatorHostClient(this);
 
   rendering_stats_instrumentation_->set_record_rendering_stats(
@@ skipping 848 matching lines @@
 
 void LayerTreeHost::SetDeviceColorSpace(
     const gfx::ColorSpace& device_color_space) {
   if (device_color_space_ == device_color_space)
     return;
   device_color_space_ = device_color_space;
   LayerTreeHostCommon::CallFunctionForEveryLayer(
       this, [](Layer* layer) { layer->SetNeedsDisplay(); });
 }
 
+void LayerTreeHost::SetContentSourceId(uint32_t id) {
+  if (content_source_id_ == id)
+    return;
+  content_source_id_ = id;
+  SetNeedsCommit();
+}
+
 void LayerTreeHost::RegisterLayer(Layer* layer) {
   DCHECK(!LayerById(layer->id()));
   DCHECK(!in_paint_layer_contents_);
   layer_id_map_[layer->id()] = layer;
   if (layer->element_id()) {
     mutator_host_->RegisterElement(layer->element_id(),
                                    ElementListType::ACTIVE);
   }
 }
 
@@ skipping 150 matching lines @@
   tree_impl->set_bottom_controls_height(bottom_controls_height_);
   tree_impl->PushBrowserControlsFromMainThread(top_controls_shown_ratio_);
   tree_impl->elastic_overscroll()->PushFromMainThread(elastic_overscroll_);
   if (tree_impl->IsActiveTree())
     tree_impl->elastic_overscroll()->PushPendingToActive();
 
   tree_impl->set_painted_device_scale_factor(painted_device_scale_factor_);
 
   tree_impl->SetDeviceColorSpace(device_color_space_);
 
+  tree_impl->set_content_source_id(content_source_id_);
+
   if (pending_page_scale_animation_) {
     tree_impl->SetPendingPageScaleAnimation(
         std::move(pending_page_scale_animation_));
   }
 
   DCHECK(!tree_impl->ViewportSizeInvalid());
 
   tree_impl->set_has_ever_been_drawn(false);
 }
 
@@ skipping 153 matching lines @@
 LayerListReverseIterator<Layer> LayerTreeHost::rend() {
   return LayerListReverseIterator<Layer>(nullptr);
 }
 
 void LayerTreeHost::SetNeedsDisplayOnAllLayers() {
   for (auto* layer : *this)
     layer->SetNeedsDisplay();
 }
 
 }  // namespace cc