ui: Cleanup class/struct forward declarations

ui/message_center/views/message_center_view.h

 // Copyright (c) 2013 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_MESSAGE_CENTER_VIEWS_MESSAGE_CENTER_VIEW_H_
 #define UI_MESSAGE_CENTER_VIEWS_MESSAGE_CENTER_VIEW_H_
 
 #include <stddef.h>
 
 #include "base/macros.h"
@@ skipping 10 matching lines @@
 }  // namespace gfx
 
 namespace message_center {
 
 class MessageCenter;
 class MessageCenterButtonBar;
 class MessageCenterTray;
 class MessageView;
 class MessageViewContextMenuController;
 class MessageListView;
-class NotificationView;
 class NotifierSettingsView;
 
 // Container for all the top-level views in the notification center, such as the
 // button bar, settings view, scrol view, and message list view.  Acts as a
 // controller for the message list view, passing data back and forth to message
 // center.
 class MESSAGE_CENTER_EXPORT MessageCenterView : public views::View,
                                                 public MessageCenterObserver,
                                                 public MessageCenterController,
                                                 public gfx::AnimationDelegate {
@@ skipping 104 matching lines @@
   Mode mode_ = Mode::BUTTONS_ONLY;
 
   std::unique_ptr<MessageViewContextMenuController> context_menu_controller_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageCenterView);
 };
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_VIEWS_MESSAGE_CENTER_VIEW_H_