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

content/public/browser/battery_status_provider.cc

+// 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.
+
+#include "content/public/browser/battery_status_provider.h"
+
+namespace content {
+
+BatteryStatusProvider* BatteryStatusProvider::GetInstance() {
+  return Singleton<BatteryStatusProvider>::get();
+}
+
+void BatteryStatusProvider::AddObserver(BatteryStatusProvider::Observer* obs) {
+  observers_.AddObserver(obs);
+}
+
+void BatteryStatusProvider::RemoveObserver(
+    BatteryStatusProvider::Observer* obs) {
+  observers_.RemoveObserver(obs);
+}
+
+void BatteryStatusProvider::SendUpdate(const PowerSupplyStatus& status) {
+  FOR_EACH_OBSERVER(Observer, observers_, PowerChanged(status));
+}
+
+BatteryStatusProvider::BatteryStatusProvider() {
+}
+
+BatteryStatusProvider::~BatteryStatusProvider() {
+}
+
+}  // namespace content