Remove external BitmapImage lazy decoding tracking

Source/platform/graphics/ImageSource.cpp

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp.toker@collabora.co.uk>
  * Copyright (C) 2008, 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 125 matching lines @@
 bool ImageSource::frameHasAlphaAtIndex(size_t index) const
 {
     return !m_decoder || m_decoder->frameHasAlphaAtIndex(index);
 }
 
 bool ImageSource::frameIsCompleteAtIndex(size_t index) const
 {
     return m_decoder && m_decoder->frameIsCompleteAtIndex(index);
 }
 
-bool ImageSource::frameIsLazyDecodedAtIndex(size_t index) const
-{
-    return m_decoder && m_decoder->frameIsCachedAndLazyDecodedAtIndex(index);
-}
-
 size_t ImageSource::frameBytesAtIndex(size_t index) const
 {
     return m_decoder ? m_decoder->frameBytesAtIndex(index) : 0;
 }
 
 } // namespace blink