chrome: Cleanup class/struct forward declarations

chrome/browser/ui/webui/chromeos/login/base_screen_handler.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 CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_BASE_SCREEN_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_BASE_SCREEN_HANDLER_H_
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/macros.h"
 #include "chrome/browser/chromeos/login/screens/model_view_channel.h"
 #include "chrome/browser/ui/webui/chromeos/login/oobe_screen.h"
 #include "components/login/base_screen_handler_utils.h"
 #include "content/public/browser/web_ui.h"
 #include "content/public/browser/web_ui_message_handler.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace base {
 class DictionaryValue;
 class ListValue;
-class Value;
 }
 
 namespace login {
 class LocalizedValuesBuilder;
 }
 
 namespace chromeos {
 
 class BaseScreen;
 class OobeUI;
@@ skipping 160 matching lines @@
 
   // Pending changes to context which will be sent when the page will be ready.
   base::DictionaryValue pending_context_changes_;
 
   DISALLOW_COPY_AND_ASSIGN(BaseScreenHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_BASE_SCREEN_HANDLER_H_