ash: Cleanup class/struct forward declarations

ash/common/system/tray/tray_details_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 ASH_COMMON_SYSTEM_TRAY_TRAY_DETAILS_VIEW_H_
 #define ASH_COMMON_SYSTEM_TRAY_TRAY_DETAILS_VIEW_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
 #include "ash/common/system/tray/special_popup_row.h"
 #include "ash/common/system/tray/tray_constants.h"
 #include "ash/common/system/tray/view_click_listener.h"
 #include "base/macros.h"
 #include "ui/views/controls/button/button.h"
 #include "ui/views/view.h"
 
 namespace base {
 class OneShotTimer;
 }  // namespace base
 
 namespace views {
 class BoxLayout;
 class CustomButton;
 class Label;
 class ProgressBar;
-class ScrollView;
 }  // namespace views
 
 namespace ash {
 namespace test {
 class TrayDetailsViewTest;
 }  // namespace test
 
 class FixedSizedScrollView;
 class ScrollBorder;
 class SystemTrayItem;
@@ skipping 112 matching lines @@
 
   // Used to delay the transition to the default view.
   std::unique_ptr<base::OneShotTimer> transition_delay_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayDetailsView);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_TRAY_TRAY_DETAILS_VIEW_H_