ash: Use system tray mojo interface to show system update tray icon

ash/common/system/update/update_observer.h

Index: ash/common/system/update/update_observer.h
diff --git a/ash/common/system/update/update_observer.h b/ash/common/system/update/update_observer.h
deleted file mode 100644
index 3912f0dd0429cd9715471ee49e38fe4a6d1b03f8..0000000000000000000000000000000000000000
--- a/ash/common/system/update/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_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_COMMON_SYSTEM_UPDATE_UPDATE_OBSERVER_H_