ui: Cleanup class/struct forward declarations

ui/views/mus/drag_drop_client_mus.h

 // Copyright 2016 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_MUS_DRAG_DROP_CLIENT_MUS_H_
 #define UI_VIEWS_MUS_DRAG_DROP_CLIENT_MUS_H_
 
 #include "base/callback.h"
 #include "ui/aura/client/drag_drop_client.h"
 #include "ui/base/dragdrop/drag_drop_types.h"
 
 namespace aura {
 class Window;
 }
 
 namespace ui {
-class LocatedEvent;
 class OSExchangeData;
 class Window;
 }
 
 namespace views {
 
 // An aura client object that translates aura dragging methods to their
 // remote ui::Window equivalents.
 class DragDropClientMus : public aura::client::DragDropClient {
  public:
@@ skipping 20 matching lines @@
   ui::Window* ui_window_;
 
   base::Closure runloop_quit_closure_;
 
   DISALLOW_COPY_AND_ASSIGN(DragDropClientMus);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_MUS_DRAG_DROP_CLIENT_MUS_H_