ui: Cleanup class/struct forward declarations

ui/app_list/presenter/app_list_presenter.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_APP_LIST_PRESENTER_APP_LIST_PRESENTER_H_
 #define UI_APP_LIST_PRESENTER_APP_LIST_PRESENTER_H_
 
 #include <stdint.h>
 
 #include "ui/app_list/presenter/app_list_presenter_export.h"
 
-namespace aura {
-class Window;
-}
-
 namespace app_list {
 
 // Interface for showing and hiding the app list.
 class APP_LIST_PRESENTER_EXPORT AppListPresenter {
  public:
   virtual ~AppListPresenter() {}
 
   // Show/hide app list window. The |window| is used to deterime in
   // which display (in which the |window| exists) the app list should
   // be shown.
@@ skipping 10 matching lines @@
   virtual bool IsVisible() const = 0;
 
   // Returns target visibility. This may differ from IsVisible() if a
   // visibility transition is in progress.
   virtual bool GetTargetVisibility() const = 0;
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_PRESENTER_APP_LIST_PRESENTER_H_