Use Shadow DOM to display fallback content for images

Source/platform/image-decoders/png/PNGImageDecoder.cpp

 /*
  * Copyright (C) 2006 Apple Computer, Inc.
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  *
  * Portions are Copyright (C) 2001 mozilla.org
  *
  * Other contributors:
  *   Stuart Parmenter <stuart@mozilla.com>
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 124 matching lines @@
         m_interlaceBuffer = 0;
         m_readOffset = 0;
     }
 
     bool decode(const SharedBuffer& data, bool sizeOnly)
     {
         m_decodingSizeOnly = sizeOnly;
         PNGImageDecoder* decoder = static_cast<PNGImageDecoder*>(png_get_progressive_ptr(m_png));
 
         // We need to do the setjmp here. Otherwise bad things will happen.
+        // The libpng manual points out: ".. there are some uncertainties about the status of local variables after a longjmp, so the
+        // user may want to be careful about doing anything after setjmp returns non-zero besides returning itself." This is why
+        // we avoid referencing |decoder| in the event of an error.
         if (setjmp(JMPBUF(m_png)))
-            return decoder->setFailed();
+            return static_cast<PNGImageDecoder*>(png_get_progressive_ptr(m_png))->setFailed();
 
         const char* segment;
         while (unsigned segmentLength = data.getSomeData(segment, m_readOffset)) {
             m_readOffset += segmentLength;
             m_currentBufferSize = m_readOffset;
             png_process_data(m_png, m_info, reinterpret_cast<png_bytep>(const_cast<char*>(segment)), segmentLength);
             // We explicitly specify the superclass isSizeAvailable() because we
             // merely want to check if we've managed to set the size, not
             // (recursively) trigger additional decoding if we haven't.
             if (sizeOnly ? decoder->ImageDecoder::isSizeAvailable() : decoder->isComplete())
@@ skipping 384 matching lines @@
     // has failed.
     if (!m_reader->decode(*m_data, onlySize) && isAllDataReceived())
         setFailed();
     // If we're done decoding the image, we don't need the PNGImageReader
     // anymore.  (If we failed, |m_reader| has already been cleared.)
     else if (isComplete())
         m_reader.clear();
 }
 
 } // namespace blink