chromeos: Add support for the battery status API on chromeos.

chrome/browser/chromeos/battery_status_provider_chromeos.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 CHROME_BROWSER_CHROMEOS_BATTERY_STATUS_PROVIDER_CHROMEOS_H_
+#define CHROME_BROWSER_CHROMEOS_BATTERY_STATUS_PROVIDER_CHROMEOS_H_
+
+#include "base/memory/singleton.h"
+#include "chromeos/dbus/power_manager_client.h"
+
+// This is a singleton object that receives battery information from the system
+// and feeds the data to content.
+class BatteryStatusProviderChromeos
+    : public chromeos::PowerManagerClient::Observer {
+ public:
+  static BatteryStatusProviderChromeos* GetInstance();
+
+ private:
+  friend struct DefaultSingletonTraits<BatteryStatusProviderChromeos>;
+
+  BatteryStatusProviderChromeos();
+  virtual ~BatteryStatusProviderChromeos();
+
+  // Overridden from chromeos::PowerManagerClient::Observer.
+  virtual void PowerChanged(const chromeos::PowerSupplyStatus& status) OVERRIDE;
+
+  DISALLOW_COPY_AND_ASSIGN(BatteryStatusProviderChromeos);
+};
+
+#endif  // CHROME_BROWSER_CHROMEOS_BATTERY_STATUS_PROVIDER_CHROMEOS_H_