(Reland) Discard compositor frames from unloaded web content

cc/trees/layer_tree_host.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_H_
 #define CC_TREES_LAYER_TREE_HOST_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 291 matching lines @@
   bool HasPendingPageScaleAnimation() const;
 
   void SetDeviceScaleFactor(float device_scale_factor);
   float device_scale_factor() const { return device_scale_factor_; }
 
   void SetPaintedDeviceScaleFactor(float painted_device_scale_factor);
   float painted_device_scale_factor() const {
     return painted_device_scale_factor_;
   }
 
+  void SetContentSourceId(uint32_t);
+  uint32_t content_source_id() const { return content_source_id_; }
+
   void SetDeviceColorSpace(const gfx::ColorSpace& device_color_space);
   const gfx::ColorSpace& device_color_space() const {
     return device_color_space_;
   }
 
   // Used externally by blink for setting the PropertyTrees when
   // |settings_.use_layer_lists| is true. This is a SPV2 setting.
   PropertyTrees* property_trees() { return &property_trees_; }
 
   void SetNeedsDisplayOnAllLayers();
@@ skipping 241 matching lines @@
 
   float bottom_controls_height_ = 0.f;
 
   float device_scale_factor_ = 1.f;
   float painted_device_scale_factor_ = 1.f;
   float page_scale_factor_ = 1.f;
   float min_page_scale_factor_ = 1.f;
   float max_page_scale_factor_ = 1.f;
   gfx::ColorSpace device_color_space_;
 
+  uint32_t content_source_id_;
+
   SkColor background_color_ = SK_ColorWHITE;
   bool has_transparent_background_ = false;
 
   LayerSelection selection_;
 
   gfx::Size device_viewport_size_;
 
   bool have_scroll_event_handlers_ = false;
   EventListenerProperties event_listener_properties_[static_cast<size_t>(
       EventListenerClass::kNumClasses)];
@@ skipping 21 matching lines @@
   bool in_update_property_trees_ = false;
 
   MutatorHost* mutator_host_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_H_