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

content/browser/battery_status/battery_status_provider_impl.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/browser/battery_status/battery_status_provider_impl.h"
+
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/power_supply_status.h"
+
+namespace content {
+
+BatteryStatusProvider* BatteryStatusProvider::GetInstance() {
+  return BatteryStatusProviderImpl::GetInstance();
+}
+
+BatteryStatusProviderImpl* BatteryStatusProviderImpl::GetInstance() {
+  return Singleton<BatteryStatusProviderImpl>::get();
+}
+
+void BatteryStatusProviderImpl::AddObserver(
+    BatteryStatusProviderImpl::Observer* obs) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  observers_.AddObserver(obs);
+}
+
+void BatteryStatusProviderImpl::RemoveObserver(
+    BatteryStatusProviderImpl::Observer* obs) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  observers_.RemoveObserver(obs);
+}
+
+void BatteryStatusProviderImpl::SendUpdate(
+    const PowerSupplyStatus& status) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  FOR_EACH_OBSERVER(Observer, observers_, PowerChanged(status));

[jam, 2012/04/13 00:46:42]

so observers_ is written on IO thread and read on UI? that'll lead to crashes...

[sadrul, 2012/04/13 11:28:44]

Ouch! Changed to use ObserverListThreadSafe instead. Should be safe?

+}
+
+BatteryStatusProviderImpl::BatteryStatusProviderImpl() {
+}
+
+BatteryStatusProviderImpl::~BatteryStatusProviderImpl() {
+}
+
+}  // namespace content