ash: Cleanup class/struct forward declarations

ash/common/system/tray/special_popup_row.h

 // Copyright (c) 2013 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_SPECIAL_POPUP_ROW_H_
 #define ASH_COMMON_SYSTEM_TRAY_SPECIAL_POPUP_ROW_H_
 
 #include "ash/ash_export.h"
 #include "ash/common/login_status.h"
 #include "ash/resources/vector_icons/vector_icons.h"
 #include "base/macros.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/views/view.h"
 
 namespace ash {
-class ThrobberView;
-class TrayItemView;
-class TrayPopupHeaderButton;
 class ViewClickListener;
 
 // Not used in material design. This class represents the bottom row of
 // detailed views and the bottom row of the system menu (date, help, power,
 // and lock). This row has a fixed height.
 // TODO(tdanderson): Remove this class when material design is enabled by
 // default. See crbug.com/614453.
 class ASH_EXPORT SpecialPopupRow : public views::View {
  public:
   SpecialPopupRow();
@@ skipping 32 matching lines @@
 
   // The container for the views positioned after |content_|.
   views::View* views_after_content_container_;
 
   DISALLOW_COPY_AND_ASSIGN(SpecialPopupRow);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_TRAY_SPECIAL_POPUP_ROW_H_