chromeos: Remove UpdateObserver, which has been unused for long.

chrome/browser/chromeos/update_observer.h

-// Copyright (c) 2010 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 CHROME_BROWSER_CHROMEOS_UPDATE_OBSERVER_H_
-#define CHROME_BROWSER_CHROMEOS_UPDATE_OBSERVER_H_
-#pragma once
-
-#include "base/basictypes.h"
-#include "base/time.h"
-#include "chrome/browser/chromeos/cros/update_library.h"
-#include "chrome/browser/chromeos/notifications/system_notification.h"
-
-class Profile;
-
-namespace chromeos {
-
-// The update observer displays a system notification when the an update is
-// available.
-
-class UpdateObserver : public UpdateLibrary::Observer {
- public:
-  explicit UpdateObserver(Profile* profile);
-  virtual ~UpdateObserver();
-
- private:
-  virtual void UpdateStatusChanged(UpdateLibrary* library);
-
-  SystemNotification notification_;
-
-  DISALLOW_COPY_AND_ASSIGN(UpdateObserver);
-};
-
-}  // namespace chromeos
-
-#endif  // CHROME_BROWSER_CHROMEOS_UPDATE_OBSERVER_H_
-