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

Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * 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 416 matching lines @@
 
     if (is3D() && paintsIntoCanvasBuffer())
         m_context->markLayerComposited();
 }
 
 bool HTMLCanvasElement::is3D() const
 {
     return m_context && m_context->is3d();
 }
 
+bool HTMLCanvasElement::isAnimated2D() const
+{
+    return m_context && m_context->is2d() && hasImageBuffer() && m_imageBuffer->wasDrawnToAfterSnapshot();
+}
+
 void HTMLCanvasElement::setSurfaceSize(const IntSize& size)
 {
     m_size = size;
     m_didFailToCreateImageBuffer = false;
     discardImageBuffer();
     clearCopiedImage();
     if (m_context && m_context->is2d() && m_context->isContextLost()) {
         m_context->didSetSurfaceSize();
     }
 }
@@ skipping 445 matching lines @@
 {
     return FloatSize(width(), height());
 }
 
 bool HTMLCanvasElement::isOpaque() const
 {
     return m_context && !m_context->hasAlpha();
 }
 
 } // blink