Move overdraw tracking code from GraphicsContext to CanvasRenderingContext2D

Source/platform/graphics/ImageBuffer.h

 /*
  * Copyright (C) 2006 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. 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.
@@ skipping 96 matching lines @@
 
     // Called at the end of a task that rendered a whole frame
     void finalizeFrame(const FloatRect &dirtyRect);
     void didFinalizeFrame();
 
     bool isDirty();
 
     const SkBitmap& bitmap() const;
 
     void willAccessPixels() { m_surface->willAccessPixels(); }
+    void willOverwriteCanvas() { m_surface->willOverwriteCanvas(); }
 
     PassRefPtr<Image> copyImage(BackingStoreCopy = CopyBackingStore, ScaleBehavior = Scaled) const;
     // Give hints on the faster copyImage Mode, return DontCopyBackingStore if it supports the DontCopyBackingStore behavior
     // or return CopyBackingStore if it doesn't.
     static BackingStoreCopy fastCopyImageMode();
 
     bool getImageData(Multiply, const IntRect&, WTF::ArrayBufferContents&) const;
 
     void putByteArray(Multiply, const unsigned char* source, const IntSize& sourceSize, const IntRect& sourceRect, const IntPoint& destPoint);
 
@@ skipping 40 matching lines @@
     unsigned char* pixels() const { return m_data; }
     int height() const { return m_size.height(); }
     int width() const { return m_size.width(); }
     unsigned char* m_data;
     IntSize m_size;
 };
 
 } // namespace blink
 
 #endif // ImageBuffer_h