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

ash/system/user/update_observer.h

Index: ash/system/user/update_observer.h
diff --git a/ash/system/user/update_observer.h b/ash/system/user/update_observer.h
deleted file mode 100644
index dacf1984dd20d568563bba8d9252d60aaa5c8745..0000000000000000000000000000000000000000
--- a/ash/system/user/update_observer.h
+++ /dev/null
@@ -1,23 +0,0 @@
-// 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_
-
-#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_