Add non-blocking frame rate limiting logic to display list 2D canvas

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 177 matching lines @@
         return m_context.get();
     }
 
     return 0;
 }
 
 void HTMLCanvasElement::didDraw(const FloatRect& rect)
 {
     clearCopiedImage();
 
+    if (hasImageBuffer())
+        m_imageBuffer->didDraw();
+
     if (RenderBox* ro = renderBox()) {
         FloatRect srcRect(0, 0, size().width(), size().height());
         FloatRect r = rect;
         r.intersect(srcRect);
         if (r.isEmpty() || m_dirtyRect.contains(r))
             return;
         m_dirtyRect.unite(r);
         FloatRect mappedDirtyRect = mapRect(r, srcRect, ro->contentBoxRect());
 
         ro->invalidatePaintRectangle(enclosingIntRect(mappedDirtyRect));
@@ skipping 505 matching lines @@
 {
     return !originClean();
 }
 
 FloatSize HTMLCanvasElement::sourceSize() const
 {
     return FloatSize(width(), height());
 }
 
 }