ash: Cleanup class/struct forward declarations

ash/common/system/date/tray_date.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_DATE_TRAY_DATE_H_
 #define ASH_COMMON_SYSTEM_DATE_TRAY_DATE_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
 #include "ash/common/login_status.h"
 #include "ash/common/system/date/clock_observer.h"
 #include "ash/common/system/tray/system_tray_item.h"
 #include "base/macros.h"
 
-namespace views {
-class Label;
-}
-
 namespace ash {
 class DateDefaultView;
 #if defined(OS_CHROMEOS)
 class SystemClockObserver;
 #endif
 
 namespace tray {
 class TimeView;
 }
 
@@ skipping 45 matching lines @@
 #if defined(OS_CHROMEOS)
   std::unique_ptr<SystemClockObserver> system_clock_observer_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(TrayDate);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_DATE_TRAY_DATE_H_