Make OffscreenCanvas animation in sync with its placeholder canvas's parent frame rate

third_party/WebKit/public/platform/WebLayerTreeView.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 15 matching lines @@
 #ifndef WebLayerTreeView_h
 #define WebLayerTreeView_h
 
 #include "WebBrowserControlsState.h"
 #include "WebColor.h"
 #include "WebCommon.h"
 #include "WebCompositorMutatorClient.h"
 #include "WebEventListenerProperties.h"
 #include "WebFloatPoint.h"
 #include "WebSize.h"
+#include "cc/surfaces/frame_sink_id.h"
 
 namespace cc {
 class AnimationHost;
 }
 
 namespace blink {
 
 class WebCompositeAndReadbackAsyncCallback;
 class WebLayer;
 class WebLayoutAndPaintAsyncCallback;
@@ skipping 109 matching lines @@
 
   // For when the embedder itself change scales on the page (e.g. devtools)
   // and wants all of the content at the new scale to be crisp.
   virtual void forceRecalculateRasterScales() {}
 
   // Input properties ---------------------------------------------------
   virtual void setEventListenerProperties(WebEventListenerClass,
                                           WebEventListenerProperties){};
   virtual void setHaveScrollEventHandlers(bool){};
 
+  // Returns the FrameSinkId of the current content::RenderWidget
+  virtual cc::FrameSinkId getFrameSinkId() { return cc::FrameSinkId(); }

[dcheng, 2017/01/23 21:53:32]

It's a bit of a layering violation to refer to content here.

Perhaps... "FrameSinkId of the widget associated with this layer tree view."?

[xlai (Olivia), 2017/01/24 20:54:12]

Done.

+
   // Debugging / dangerous ---------------------------------------------
 
   virtual WebEventListenerProperties eventListenerProperties(
       WebEventListenerClass) const {
     return WebEventListenerProperties::Nothing;
   };
   virtual bool haveScrollEventHandlers() const { return false; };
 
   virtual int layerTreeId() const { return 0; }
 
   // Toggles the FPS counter in the HUD layer
   virtual void setShowFPSCounter(bool) {}
 
   // Toggles the paint rects in the HUD layer
   virtual void setShowPaintRects(bool) {}
 
   // Toggles the debug borders on layers
   virtual void setShowDebugBorders(bool) {}
 
   // Toggles scroll bottleneck rects on the HUD layer
   virtual void setShowScrollBottleneckRects(bool) {}
 };
 
 }  // namespace blink
 
 #endif  // WebLayerTreeView_h