ash: Cleanup class/struct forward declarations

ash/common/system/tray_accessibility.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_ACCESSIBILITY_H_
 #define ASH_COMMON_SYSTEM_TRAY_ACCESSIBILITY_H_
 
 #include <stdint.h>
 
 #include "ash/common/accessibility_delegate.h"
@@ skipping 10 matching lines @@
 class TrayAccessibilityTest;
 }
 
 namespace gfx {
 struct VectorIcon;
 }
 
 namespace views {
 class Button;
 class CustomButton;
-class ImageView;
 class Label;
 class View;
 }
 
 namespace ash {
 class HoverHighlightView;
 class SystemTrayItem;
 
 namespace tray {
 
@@ skipping 105 matching lines @@
   // A11y feature status on just entering the lock screen.
   bool show_a11y_menu_on_lock_screen_;
 
   friend class chromeos::TrayAccessibilityTest;
   DISALLOW_COPY_AND_ASSIGN(TrayAccessibility);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_TRAY_ACCESSIBILITY_H_