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

Source/platform/graphics/ImageFrameGenerator.cpp

 /*
  * Copyright (C) 2012 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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 306 matching lines @@
 }
 
 bool ImageFrameGenerator::hasAlpha(size_t index)
 {
     MutexLocker lock(m_alphaMutex);
     if (index < m_hasAlpha.size())
         return m_hasAlpha[index];
     return true;
 }
 
-} // namespace
+} // namespace blink