2D canvas: remain in deferred rendering mode with canvas to canvas drawImage

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 64 matching lines @@
 
     void setClient(ImageBufferClient* client) { m_client = client; }
 
     const IntSize& size() const { return m_surface->size(); }
     bool isAccelerated() const { return m_surface->isAccelerated(); }
     bool isRecording() const { return m_surface->isRecording(); }
     void setHasExpensiveOp() { m_surface->setHasExpensiveOp(); }
     bool isExpensiveToPaint() const { return m_surface->isExpensiveToPaint(); }
     bool isSurfaceValid() const;
     bool restoreSurface() const;
-    void didDraw(const FloatRect& rect) const { m_surface->didDraw(rect); }
+    void didDraw(const FloatRect&) const;
+    bool wasDrawnToAfterSnapshot() const { return m_snapshotState == DrawnToAfterSnapshot; }
 
     void setFilterQuality(SkFilterQuality filterQuality) { m_surface->setFilterQuality(filterQuality); }
     void setIsHidden(bool hidden) { m_surface->setIsHidden(hidden); }
 
     // Called by subclasses of ImageBufferSurface to install a new canvas object
     void resetCanvas(SkCanvas*) const;
 
     SkCanvas* canvas() const;
     void disableDeferral() const;
 
@@ skipping 35 matching lines @@
     PassRefPtr<Image> newImageSnapshot() const;
 
     DisplayItemClient displayItemClient() const { return toDisplayItemClient(this); }
     String debugName() const { return "ImageBuffer"; }
 
     void draw(GraphicsContext*, const FloatRect&, const FloatRect*, SkXfermode::Mode);
 
 private:
     ImageBuffer(PassOwnPtr<ImageBufferSurface>);
 
+    enum SnapshotState {
+        InitialSnapshotState,
+        DidAcquireSnapshot,
+        DrawnToAfterSnapshot,
+    };
+    mutable SnapshotState m_snapshotState;
     OwnPtr<ImageBufferSurface> m_surface;
     ImageBufferClient* m_client;
 };
 
 struct ImageDataBuffer {
     ImageDataBuffer(const IntSize& size, unsigned char* data) : m_data(data), m_size(size) { }
     String PLATFORM_EXPORT toDataURL(const String& mimeType, const double* quality) const;
     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