ui: Cleanup class/struct forward declarations

ui/views/bubble/tray_bubble_view.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_VIEWS_BUBBLE_TRAY_BUBBLE_VIEW_H_
 #define UI_VIEWS_BUBBLE_TRAY_BUBBLE_VIEW_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "ui/views/bubble/bubble_dialog_delegate.h"
 #include "ui/views/mouse_watcher.h"
 #include "ui/views/views_export.h"
 
-namespace ui {
-class LocatedEvent;
-}
-
 namespace views {
 class View;
 class Widget;
 }
 
 namespace views {
 
 namespace internal {
 class TrayBubbleBorder;
 class TrayBubbleContentMask;
@@ skipping 178 matching lines @@
 
   // Used to find any mouse movements.
   std::unique_ptr<MouseWatcher> mouse_watcher_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayBubbleView);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_BUBBLE_TRAY_BUBBLE_VIEW_H_