mash: Move SystemTrayDelegate and dependencies to //ash/common

ash/common/system/update/update_observer.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_SYSTEM_USER_UPDATE_OBSERVER_H_
-#define ASH_SYSTEM_USER_UPDATE_OBSERVER_H_
+#ifndef ASH_COMMON_SYSTEM_UPDATE_UPDATE_OBSERVER_H_
+#define ASH_COMMON_SYSTEM_UPDATE_UPDATE_OBSERVER_H_
 
 #include "ash/ash_export.h"
 
 namespace ash {
 
 struct UpdateInfo;
 
 class ASH_EXPORT UpdateObserver {
  public:
   virtual ~UpdateObserver() {}
 
   virtual void OnUpdateRecommended(const UpdateInfo& info) = 0;
 };
 
 }  // namespace ash
 
-#endif  //ASH_SYSTEM_USER_UPDATE_OBSERVER_H_
+#endif  //ASH_COMMON_SYSTEM_UPDATE_UPDATE_OBSERVER_H_