ui: Cleanup class/struct forward declarations

ui/message_center/views/message_list_view.h

 // Copyright (c) 2015 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_LIST_VIEW_H_
 #define UI_MESSAGE_CENTER_VIEWS_MESSAGE_LIST_VIEW_H_
 
 #include <list>
 #include <set>
 
 #include "base/macros.h"
 #include "ui/compositor/paint_context.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/message_center/message_center_export.h"
 #include "ui/message_center/notification.h"
 #include "ui/views/animation/bounds_animator.h"
 #include "ui/views/animation/bounds_animator_observer.h"
 #include "ui/views/view.h"
 
-namespace gfx {
-class Canvas;
-}
-
 namespace ui {
 class Layer;
 }
 
 namespace message_center {
 
 class MessageCenterView;
 class MessageView;
 
 // Displays a list of messages for rich notifications. Functions as an array of
@@ skipping 70 matching lines @@
   // If true, the message loop will be quitted after the animation finishes.
   // This is just for tests and has no setter.
   bool quit_message_loop_after_animation_for_test_;
 
   base::WeakPtrFactory<MessageListView> weak_ptr_factory_;
   DISALLOW_COPY_AND_ASSIGN(MessageListView);
 };
 
 }  // namespace message_center
 #endif  // UI_MESSAGE_CENTER_VIEWS_MESSAGE_LIST_VIEW_H_