Created multi-process-friendly PowerMonitor interface.

content/browser/power_monitor_message_broadcaster.h

+// Copyright 2013 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 CONTENT_BROWSER_POWER_MONITOR_MESSAGE_BROADCASTER_H_
+#define CONTENT_BROWSER_POWER_MONITOR_MESSAGE_BROADCASTER_H_
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "base/power_monitor/power_observer.h"
+#include "content/common/content_export.h"
+#include "content/public/browser/browser_message_filter.h"
+#include "content/public/browser/browser_thread.h"
+
+
+namespace IPC {
+  class Sender;

[jam, 2013/07/30 23:52:00]

nit: no need, since you're including browser_message_filter which by definition
derives from this. also extra blank line above

+}
+
+namespace content {
+
+// A class used to monitor the power state change and communicate it to child
+// processes via IPC. All interaction with this class must be done on the UI
+// thread.

[jam, 2013/07/30 23:52:00]

when you say all interactions, do you mean also construction? because
BrowserChildProcessHostImpl is creating this on the IO thread

+class CONTENT_EXPORT PowerMonitorMessageBroadcaster
+    : public base::PowerObserver {
+public:

[jam, 2013/07/30 23:52:00]

nit: here and below, space before public

+  explicit PowerMonitorMessageBroadcaster(IPC::Sender* sender);
+  virtual ~PowerMonitorMessageBroadcaster();
+
+  // Implement PowerObserver.
+  virtual void OnPowerStateChange(bool on_battery_power) OVERRIDE;
+  virtual void OnSuspend() OVERRIDE;
+  virtual void OnResume() OVERRIDE;
+
+private:
+  IPC::Sender* sender_;
+
+  DISALLOW_COPY_AND_ASSIGN(PowerMonitorMessageBroadcaster);
+};
+
+}  // namespace base
+
+#endif  // CONTENT_BROWSER_POWER_MONITOR_MESSAGE_BROADCASTER_H_