mash: Migrate tray date view to //ash/common types

ash/common/system/tray/wm_system_tray_notifier.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 ASH_COMMON_SYSTEM_TRAY_WM_SYSTEM_TRAY_NOTIFIER_H_
 #define ASH_COMMON_SYSTEM_TRAY_WM_SYSTEM_TRAY_NOTIFIER_H_
 
 #include "ash/ash_export.h"
 #include "base/macros.h"
 #include "base/observer_list.h"
 
 namespace ash {
 
+class ClockObserver;
 struct UpdateInfo;
 class UpdateObserver;
 
 // Observer and notification manager for the ash system tray. This version
 // contains the observers that have been ported to //ash/common. See also
 // ash::SystemTrayNotifier.
 // TODO(jamescook): After all the observers have been moved, rename this class
 // to SystemTrayNotifier.
 class ASH_EXPORT WmSystemTrayNotifier {
  public:
   WmSystemTrayNotifier();
   ~WmSystemTrayNotifier();
 
+  void AddClockObserver(ClockObserver* observer);
+  void RemoveClockObserver(ClockObserver* observer);
+
   void AddUpdateObserver(UpdateObserver* observer);
   void RemoveUpdateObserver(UpdateObserver* observer);
 
+  void NotifyRefreshClock();
+  void NotifyDateFormatChanged();
+  void NotifySystemClockTimeUpdated();
+  void NotifySystemClockCanSetTimeChanged(bool can_set_time);
+
   void NotifyUpdateRecommended(const UpdateInfo& info);
 
  private:
+  base::ObserverList<ClockObserver> clock_observers_;
   base::ObserverList<UpdateObserver> update_observers_;
 
   DISALLOW_COPY_AND_ASSIGN(WmSystemTrayNotifier);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_TRAY_WM_SYSTEM_TRAY_NOTIFIER_H_