Move low battery notification to Message Center.

ash/system/chromeos/power/battery_notification.h

+// Copyright 2015 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_CHROMEOS_POWER_BATTERY_NOTIFICATION_H_
+#define ASH_SYSTEM_CHROMEOS_POWER_BATTERY_NOTIFICATION_H_
+
+#include "ash/ash_export.h"
+#include "ash/system/chromeos/power/tray_power.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace message_center {
+class MessageCenter;
+}
+
+namespace ash {
+
+// Class for showing and hiding a MessageCenter low battery notification.
+class ASH_EXPORT BatteryNotification {
+ public:
+  BatteryNotification(message_center::MessageCenter* message_center);
+
+  // Shows the notification, ensuring that new notifications are made visible
+  // by removing rather than updating them in the MessageCenter.
+  void Show(TrayPower::NotificationState notification_state);
+  // Removes the notification.
+  void Hide();
+  // Updates an existing notification.
+  void Update(TrayPower::NotificationState notification_state);
+
+ private:
+  message_center::MessageCenter* message_center_;
+
+  DISALLOW_COPY_AND_ASSIGN(BatteryNotification);
+};
+
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_CHROMEOS_POWER_BATTERY_NOTIFICATION_H_