Allow frames to be free'd even for static images

Source/platform/image-decoders/ImageDecoder.cpp

 /*
  * Copyright (C) Research In Motion Limited 2009-2010. 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
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 116 matching lines @@
 unsigned ImageDecoder::frameBytesAtIndex(size_t index) const
 {
     if (m_frameBufferCache.size() <= index || m_frameBufferCache[index].status() == ImageFrame::FrameEmpty)
         return 0;
     // FIXME: Use the dimension of the requested frame.
     return m_size.area() * sizeof(ImageFrame::PixelData);
 }
 
 size_t ImageDecoder::clearCacheExceptFrame(size_t clearExceptFrame)
 {
-    // Don't clear if there are no frames or only one frame.
-    if (m_frameBufferCache.size() <= 1)
+    // Don't clear if there are no frames or only one frame, and we're not
+    // specifically requested to clear all frames.
+    if (m_frameBufferCache.size() <= 1 && clearExceptFrame != kNotFound)
         return 0;

[Peter Kasting, 2014/01/14 00:46:18]

Nit: Can't we just implement this by removing this block entirely?  It seems
like the code below will already do what we want in this case, if only we didn't
have this condition.

[fs, 2014/01/14 08:32:09]

Yes, true. Will drop this block.

 
     size_t frameBytesCleared = 0;
     for (size_t i = 0; i < m_frameBufferCache.size(); ++i) {
         if (i != clearExceptFrame) {
             frameBytesCleared += frameBytesAtIndex(i);
             clearFrameBuffer(i);
         }
     }
     return frameBytesCleared;
 }
@@ skipping 42 matching lines @@
         // Otherwise, the previous frame contributes to this frame.
         return (prevBuffer->originalFrameRect().contains(IntRect(IntPoint(), size()))
             || (prevBuffer->requiredPreviousFrameIndex() == kNotFound)) ? kNotFound : prevFrame;
     default:
         ASSERT_NOT_REACHED();
         return kNotFound;
     }
 }
 
 } // namespace WebCore