Reland again "Decode GIF image frames on demand".

Source/core/platform/image-decoders/ico/ICOImageDecoder.cpp

 /*
  * Copyright (c) 2008, 2009, Google Inc. All rights reserved.
  * 
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  * 
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 84 matching lines @@
     // The size calculated inside the BMPImageReader had better match the one in
     // the icon directory.
     return m_frameSize.isEmpty() ? ImageDecoder::setSize(width, height) : ((IntSize(width, height) == m_frameSize) || setFailed());
 }
 
 size_t ICOImageDecoder::frameCount()
 {
     decode(0, true);
     if (m_frameBufferCache.isEmpty()) {
         m_frameBufferCache.resize(m_dirEntries.size());
-        for (size_t i = 0; i < m_dirEntries.size(); ++i)
+        for (size_t i = 0; i < m_dirEntries.size(); ++i) {
             m_frameBufferCache[i].setPremultiplyAlpha(m_premultiplyAlpha);
+            m_frameBufferCache[i].setRequiredPreviousFrameIndex(notFound);
+        }
     }
     // CAUTION: We must not resize m_frameBufferCache again after this, as
     // decodeAtIndex() may give a BMPImageReader a pointer to one of the
     // entries.
     return m_frameBufferCache.size();
 }
 
 ImageFrame* ICOImageDecoder::frameBufferAtIndex(size_t index)
 {
     // Ensure |index| is valid.
@@ skipping 111 matching lines @@
         m_pngDecoders[index] = adoptPtr(
             new PNGImageDecoder(m_premultiplyAlpha ? ImageSource::AlphaPremultiplied : ImageSource::AlphaNotPremultiplied,
                                 m_ignoreGammaAndColorProfile ? ImageSource::GammaAndColorProfileIgnored : ImageSource::GammaAndColorProfileApplied));
         setDataForPNGDecoderAtIndex(index);
     }
     // Fail if the size the PNGImageDecoder calculated does not match the size
     // in the directory.
     if (m_pngDecoders[index]->isSizeAvailable() && (m_pngDecoders[index]->size() != dirEntry.m_size))
         return setFailed();
     m_frameBufferCache[index] = *m_pngDecoders[index]->frameBufferAtIndex(0);
+    m_frameBufferCache[index].setRequiredPreviousFrameIndex(notFound);

[Peter Kasting, 2013/06/03 18:39:10]

Do you need to call setPremultiplyAlpha here as in frameCount() or is that
handled by the PNG decoder?

[Xianzhu, 2013/06/03 18:44:44]

Yes, we need it. Done.

     return !m_pngDecoders[index]->failed() || setFailed();
 }
 
 bool ICOImageDecoder::processDirectory()
 {
     // Read directory.
     ASSERT(!m_decodedOffset);
     if (m_data->size() < sizeOfDirectory)
         return false;
     const uint16_t fileType = readUint16(2);
@@ skipping 85 matching lines @@
     // Check if this entry is a BMP or a PNG; we need 4 bytes to check the magic
     // number.
     ASSERT_WITH_SECURITY_IMPLICATION(index < m_dirEntries.size());
     const uint32_t imageOffset = m_dirEntries[index].m_imageOffset;
     if ((imageOffset > m_data->size()) || ((m_data->size() - imageOffset) < 4))
         return Unknown;
     return strncmp(&m_data->data()[imageOffset], "\x89PNG", 4) ? BMP : PNG;
 }
 
 }