Add non-blocking frame rate limiting logic to display list 2D canvas

Source/platform/graphics/RecordingImageBufferSurface.h

 // Copyright 2014 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 RecordingImageBufferSurface_h
 #define RecordingImageBufferSurface_h
 
 #include "platform/graphics/ImageBufferSurface.h"
+#include "public/platform/WebThread.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/RefPtr.h"
 
 class SkPicture;
 class SkPictureRecorder;
 class RecordingImageBufferSurfaceTest;
 
 namespace blink {
 
 class GraphicsContext;
 
-class PLATFORM_EXPORT RecordingImageBufferSurface : public ImageBufferSurface {
+class PLATFORM_EXPORT RecordingImageBufferSurface : public ImageBufferSurface, public blink::WebThread::TaskObserver {
     WTF_MAKE_NONCOPYABLE(RecordingImageBufferSurface); WTF_MAKE_FAST_ALLOCATED;
 public:
     RecordingImageBufferSurface(const IntSize&, OpacityMode = NonOpaque);
     virtual ~RecordingImageBufferSurface();
 
     // Implementation of ImageBufferSurface interfaces
     virtual SkCanvas* canvas() const OVERRIDE;
     virtual PassRefPtr<SkPicture> getPicture() OVERRIDE;
     virtual bool isValid() const OVERRIDE { return true; }
     virtual void willReadback() OVERRIDE;
-    virtual void willUse() OVERRIDE;
+    virtual void didDraw() OVERRIDE;
     virtual void didClearCanvas() OVERRIDE;
     virtual void setImageBuffer(ImageBuffer*) OVERRIDE;
 
 private:
     friend class ::RecordingImageBufferSurfaceTest; // for unit testing
     void fallBackToRasterCanvas();
     void initializeCurrentFrame();
-    bool handleOpaqueFrame();
+    bool finalizeFrame();
+
+    // Implementation of WebThread::TaskObserver methods
+    virtual void willProcessTask() OVERRIDE;
+    virtual void didProcessTask() OVERRIDE;
 
     OwnPtr<SkPictureRecorder> m_currentFrame;
     RefPtr<SkPicture> m_previousFrame;
     OwnPtr<SkCanvas> m_rasterCanvas;
     GraphicsContext* m_graphicsContext;
     int m_initialSaveCount;
     bool m_frameWasCleared;
-    bool m_surfaceUsedSincePreviousFrameWasPresented;
+    bool m_recordedSinceLastFrameWasFinalized;
 };
 
 } // namespace blink
 
 #endif