Clean up forward declarations in Source/platform

Source/platform/weborigin/KURL.h

 /*
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2011, 2012 Apple 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 252 matching lines @@
 inline bool operator!=(const String& a, const KURL& b)
 {
     return a != b.string();
 }
 
 } // namespace blink
 
 namespace WTF {
 
 // KURLHash is the default hash for String
-template<typename T> struct DefaultHash;
 template<> struct DefaultHash<blink::KURL> {
     typedef blink::KURLHash Hash;
 };
 
 } // namespace WTF
 
 #endif // KURL_h