Allow eviction of ImageBitmaps that are created from ImageElements.

Source/core/loader/cache/CachedImage.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
     Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
     License as published by the Free Software Foundation; either
@@ skipping 384 matching lines @@
 void CachedImage::decodedSizeChanged(const Image* image, int delta)
 {
     if (!image || image != m_image)
         return;
 
     setDecodedSize(decodedSize() + delta);
 }
 
 void CachedImage::didDraw(const Image* image)
 {
-    if (!image || image != m_image)
+    // FIXME: not sure if this change is valid. Since taking a subset
+    // produces a different image, m_image != image for ImageBitmaps

[Justin Novosad, 2013/07/19 21:09:53]

We need a better condition. Something like !m_image.sharesDataWith(image)

+    if (!image)
         return;
 
     double timeStamp = FrameView::currentPaintTimeStamp();
     if (!timeStamp) // If didDraw is called outside of a Frame paint.
         timeStamp = currentTime();
 
     CachedResource::didAccessDecodedData(timeStamp);
 }
 
 bool CachedImage::shouldPauseAnimation(const Image* image)
@@ skipping 36 matching lines @@
 
 bool CachedImage::currentFrameKnownToBeOpaque(const RenderObject* renderer)
 {
     Image* image = imageForRenderer(renderer);
     if (image->isBitmapImage())
         image->nativeImageForCurrentFrame(); // force decode
     return image->currentFrameKnownToBeOpaque();
 }
 
 } // namespace WebCore