Remove external BitmapImage lazy decoding tracking

Source/platform/graphics/ImageSource.h

 /*
  * Copyright (C) 2004, 2005, 2006 Apple Computer, 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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 69 matching lines @@
     int repetitionCount();
 
     size_t frameCount() const;
 
     // Attempts to create the requested frame.
     PassRefPtr<SkImage> createFrameAtIndex(size_t);
 
     float frameDurationAtIndex(size_t) const;
     bool frameHasAlphaAtIndex(size_t) const; // Whether or not the frame actually used any alpha.
     bool frameIsCompleteAtIndex(size_t) const; // Whether or not the frame is fully received.
-    bool frameIsLazyDecodedAtIndex(size_t) const; // Whether or not the frame is lazy-decoded.
     ImageOrientation orientationAtIndex(size_t) const; // EXIF image orientation
 
     // Returns the number of bytes in the decoded frame. May return 0 if the
     // frame has not yet begun to decode.
     size_t frameBytesAtIndex(size_t) const;
 
 private:
     OwnPtr<DeferredImageDecoder> m_decoder;
 };
 
 } // namespace blink
 
 #endif