Use SkImage as a backing store for copying 2d Contexts to ImageBitmaps.

Source/core/platform/graphics/ImageBuffer.h

Index: Source/core/platform/graphics/ImageBuffer.h
diff --git a/Source/core/platform/graphics/ImageBuffer.h b/Source/core/platform/graphics/ImageBuffer.h
index fd96acf2fb82051d6082a9b84370ac41c21657f8..771719945363bbac3252ddc2cf00f5174b3356ba 100644
--- a/Source/core/platform/graphics/ImageBuffer.h
+++ b/Source/core/platform/graphics/ImageBuffer.h
@@ -43,6 +43,8 @@
 #include "wtf/Vector.h"
 
 class SkCanvas;
+class SkImage;
+class SkSurface;
 
 namespace WebKit { class WebLayer; }
 
@@ -104,6 +106,7 @@ public:
 
     GraphicsContext* context() const;
 
+    SkImage* imageSnapshot() const;
     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.
@@ -133,6 +136,9 @@ public:
     void reportMemoryUsage(MemoryObjectInfo*) const;
 
 private:
+    SkCanvas* createAcceleratedCanvas(const IntSize&, OwnPtr<Canvas2DLayerBridge>*, OpacityMode);
+    SkCanvas* createNonPlatformCanvas(const IntSize&);
+
     void draw(GraphicsContext*, const FloatRect&, const FloatRect& = FloatRect(0, 0, -1, -1), CompositeOperator = CompositeSourceOver, BlendMode = BlendModeNormal, bool useLowQualityScale = false);
     void drawPattern(GraphicsContext*, const FloatRect&, const FloatSize&, const FloatPoint&, CompositeOperator, const FloatRect&);
 
@@ -145,6 +151,7 @@ private:
     IntSize m_logicalSize;
     float m_resolutionScale;
     OwnPtr<SkCanvas> m_canvas;
+    RefPtr<SkSurface> m_surface;
     OwnPtr<GraphicsContext> m_context;
     OwnPtr<Canvas2DLayerBridge> m_layerBridge;