Add more missing closing namespace comments.

third_party/WebKit/Source/modules/canvas2d/CanvasGradient.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  *
  * 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
@@ skipping 41 matching lines @@
 
     Color color = 0;
     if (!parseColorOrCurrentColor(color, colorString, 0 /*canvas*/)) {
         exceptionState.throwDOMException(SyntaxError, "The value provided ('" + colorString + "') could not be parsed as a color.");
         return;
     }
 
     m_gradient->addColorStop(value, color);
 }
 
-} // namespace
+} // namespace blink