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;
+}
+
+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.
+class CONTENT_EXPORT PowerMonitorMessageBroadcaster
+    : public base::PowerObserver,
+      public base::RefCountedThreadSafe<
+          PowerMonitorMessageBroadcaster, BrowserThread::DeleteOnUIThread> {
+public:
+  explicit PowerMonitorMessageBroadcaster(IPC::Sender* sender);
+
+  // Implement PowerObserver.
+  virtual void OnPowerStateChange(bool on_battery_power) OVERRIDE;
+  virtual void OnSuspend() OVERRIDE;
+  virtual void OnResume() OVERRIDE;
+
+private:
+  friend struct BrowserThread::DeleteOnThread<BrowserThread::UI>;
+  friend class base::DeleteHelper<PowerMonitorMessageBroadcaster>;
+  virtual ~PowerMonitorMessageBroadcaster();
+
+  friend class PowerMonitorMessageFilter;
+  void RemoveSender();
+
+  IPC::Sender* sender_;
+
+  DISALLOW_COPY_AND_ASSIGN(PowerMonitorMessageBroadcaster);
+};
+
+class PowerMonitorMessageFilter : public BrowserMessageFilter {

[piman, 2013/07/29 21:18:18]

At a high level, I'm not sure why you create a filter to own the broadcaster.
Why not directly create the broadcaster in the process hosts (which already know
how to send IPCs)?

[bajones, 2013/07/29 21:33:36]

Please see @jam's two previous comments.

+public:
+  PowerMonitorMessageFilter();
+
+  virtual void OnChannelClosing() OVERRIDE;
+
+  virtual bool OnMessageReceived(
+      const IPC::Message& message,
+      bool* message_was_ok) OVERRIDE;
+
+private:
+  virtual ~PowerMonitorMessageFilter();
+
+  // These two functions must be called on the UI thread
+  void CreateBroadcaster();
+  void DisableBroadcaster();
+
+  scoped_refptr<PowerMonitorMessageBroadcaster> broadcaster_;
+};
+
+}  // namespace base
+
+#endif  // CONTENT_BROWSER_POWER_MONITOR_MESSAGE_BROADCASTER_H_