Remove gc extension from webkit/support

content/shell/renderer/gc_extension.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef WEBKIT_SUPPORT_GC_EXTENSION_H_
-#define WEBKIT_SUPPORT_GC_EXTENSION_H_
+#ifndef CONTENT_SHELL_RENDERER_GC_EXTENSION_H_
+#define CONTENT_SHELL_RENDERER_GC_EXTENSION_H_
 
 namespace v8 {
 class Extension;
 }
 
 namespace extensions_v8 {
 
 // GCExtension is a v8 extension to expose a method into JS for triggering
 // garbage collection. This should only be used for debugging.
 class GCExtension {
  public:
   static v8::Extension* Get();
 };
 
 }  // namespace extensions_v8
 
-#endif  // WEBKIT_SUPPORT_GC_EXTENSION_H_
+#endif  // CONTENT_SHELL_RENDERER_GC_EXTENSION_H_