Remove forward declarations from Source/core/dom/custom

Source/core/dom/custom/CustomElementDefinition.h

 /*
  * 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 34 matching lines @@
     const CustomElementDescriptor& descriptor() const { return m_descriptor; }
     CustomElementLifecycleCallbacks* callbacks() const { return m_callbacks.get(); }
 
 private:
     CustomElementDefinition(const CustomElementDescriptor&, PassRefPtr<CustomElementLifecycleCallbacks>);
 
     CustomElementDescriptor m_descriptor;
     RefPtr<CustomElementLifecycleCallbacks> m_callbacks;
 };
 
-}
+} // namespace blink
 
 #endif // CustomElementDefinition_h