ios: Cleanup class/struct forward declarations

ios/web/public/webui/web_ui_ios_message_handler.h

 // Copyright 2014 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 IOS_WEB_PUBLIC_WEBUI_WEB_UI_IOS_MESSAGE_HANDLER_H_
 #define IOS_WEB_PUBLIC_WEBUI_WEB_UI_IOS_MESSAGE_HANDLER_H_
 
 #include "base/strings/string16.h"
 
-class GURL;
-
 namespace base {
-class DictionaryValue;
 class ListValue;
 }
 
 namespace web {
 
 class WebUIIOS;
 class WebUIIOSImpl;
 
 // Messages sent from the DOM are forwarded via the WebUIIOS to handler
 // classes. These objects are owned by WebUIIOS and destroyed when the
@@ skipping 30 matching lines @@
  private:
   // Provide external classes access to web_ui() and set_web_ui().
   friend class WebUIIOSImpl;
 
   WebUIIOS* web_ui_;
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_PUBLIC_WEBUI_WEB_UI_IOS_MESSAGE_HANDLER_H_