Use SkImage snapshots for ImageBufferSurface texture access

Source/platform/graphics/ImageBufferSurface.h

Index: Source/platform/graphics/ImageBufferSurface.h
diff --git a/Source/platform/graphics/ImageBufferSurface.h b/Source/platform/graphics/ImageBufferSurface.h
index 50e9636d7d94abd432fd65419bbdd89f62a2898d..b6bbc276ceb00a6629efc6fbe70b0c7878e5ce66 100644
--- a/Source/platform/graphics/ImageBufferSurface.h
+++ b/Source/platform/graphics/ImageBufferSurface.h
@@ -62,11 +62,10 @@ public:
     virtual void willAccessPixels() { }
     virtual void didDraw(const FloatRect& rect) { }
     virtual bool isValid() const = 0;
-    virtual bool restore() { return false; };
-    virtual WebLayer* layer() const { return 0; };
+    virtual bool restore() { return false; }
+    virtual WebLayer* layer() const { return 0; }
     virtual bool isAccelerated() const { return false; }
     virtual bool isRecording() const { return false; }
-    virtual Platform3DObject getBackingTexture() const { return 0; }
     virtual void didModifyBackingTexture() { }
     virtual bool cachedBitmapEnabled() const { return false; }
     virtual bool isExpensiveToPaint() { return false; }
@@ -80,10 +79,15 @@ public:
     virtual void finalizeFrame(const FloatRect &dirtyRect) { }
     virtual void willDrawVideo() { }
     virtual void willOverwriteCanvas() { }
-    virtual PassRefPtr<SkImage> newImageSnapshot() const;
     virtual void draw(GraphicsContext*, const FloatRect& destRect, const FloatRect& srcRect, SkXfermode::Mode);
     virtual void setHasExpensiveOp() { }
 
+    // These methods return an SkImage representing the backing texture. We support both variants
+    // to avoid the snapshot overhead (flushing deferred draws, COW semantics, fallback in
+    // RecordingImageBufferSurface) when not strictly required.
+    virtual PassRefPtr<SkImage> newImageSnapshot() const { return nullptr; }
+    virtual PassRefPtr<SkImage> getBackingTextureImage() const { return nullptr; }
+
     OpacityMode opacityMode() const { return m_opacityMode; }
     const IntSize& size() const { return m_size; }
     void notifyIsValidChanged(bool isValid) const;