ui: Cleanup class/struct forward declarations

ui/web_dialogs/web_dialog_ui.h

 // Copyright (c) 2012 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 UI_WEB_DIALOGS_WEB_DIALOG_UI_H_
 #define UI_WEB_DIALOGS_WEB_DIALOG_UI_H_
 
 #include <string>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/strings/string16.h"
 #include "content/public/browser/web_contents_delegate.h"
 #include "content/public/browser/web_ui_controller.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/web_dialogs/web_dialogs_export.h"
 #include "url/gurl.h"
 
 namespace content {
 class WebContents;
-class WebUIMessageHandler;
-struct ContextMenuParams;
-}
-
-namespace gfx {
-class Size;
 }
 
 namespace ui {
 
 class WebDialogDelegate;
 
 // Displays file URL contents inside a modal web dialog.
 //
 // This application really should not use WebContents + WebUI. It should instead
 // just embed a RenderView in a dialog and be done with it.
@@ skipping 38 matching lines @@
 
   // JS message handler.
   void OnDialogClosed(const base::ListValue* args);
 
   DISALLOW_COPY_AND_ASSIGN(WebDialogUI);
 };
 
 }  // namespace ui
 
 #endif  // UI_WEB_DIALOGS_WEB_DIALOG_UI_H_