(Reland) Discard compositor frames from unloaded web content

cc/trees/layer_tree_impl.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_TREES_LAYER_TREE_IMPL_H_
 #define CC_TREES_LAYER_TREE_IMPL_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 211 matching lines @@
   void SetDeviceScaleFactor(float device_scale_factor);
   float device_scale_factor() const { return device_scale_factor_; }
 
   void set_painted_device_scale_factor(float painted_device_scale_factor) {
     painted_device_scale_factor_ = painted_device_scale_factor;
   }
   float painted_device_scale_factor() const {
     return painted_device_scale_factor_;
   }
 
+  void set_content_source_id(uint32_t id) { content_source_id_ = id; }
+  uint32_t content_source_id() { return content_source_id_; }
+
   void SetDeviceColorSpace(const gfx::ColorSpace& device_color_space);
   const gfx::ColorSpace& device_color_space() const {
     return device_color_space_;
   }
 
   SyncedElasticOverscroll* elastic_overscroll() {
     return elastic_overscroll_.get();
   }
   const SyncedElasticOverscroll* elastic_overscroll() const {
     return elastic_overscroll_.get();
@@ skipping 246 matching lines @@
   LayerSelection selection_;
 
   scoped_refptr<SyncedProperty<ScaleGroup>> page_scale_factor_;
   float min_page_scale_factor_;
   float max_page_scale_factor_;
 
   float device_scale_factor_;
   float painted_device_scale_factor_;
   gfx::ColorSpace device_color_space_;
 
+  uint32_t content_source_id_;
+
   scoped_refptr<SyncedElasticOverscroll> elastic_overscroll_;
 
   std::unique_ptr<OwnedLayerImplList> layers_;
   LayerImplMap layer_id_map_;
   LayerImplList layer_list_;
   // Set of layers that need to push properties.
   std::unordered_set<LayerImpl*> layers_that_should_push_properties_;
 
   std::unordered_map<ElementId, int, ElementIdHash> element_layers_map_;
 
@@ skipping 55 matching lines @@
 
   std::unique_ptr<PendingPageScaleAnimation> pending_page_scale_animation_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_IMPL_H_