Cleanup namespace usage in platform/graphics/[G-S]*

Source/platform/graphics/ImageObserver.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 30 matching lines @@
 public:
     virtual void decodedSizeChanged(const Image*, int delta) = 0;
     virtual void didDraw(const Image*) = 0;
 
     virtual bool shouldPauseAnimation(const Image*) = 0;
     virtual void animationAdvanced(const Image*) = 0;
 
     virtual void changedInRect(const Image*, const IntRect&) = 0;
 };
 
-}
+} // namespace blink
 
 #endif