add device notification to Mac

content/browser/device_monitor_mac.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 CONTENT_BROWSER_DEVICE_MONITOR_MAC_H_
+#define CONTENT_BROWSER_DEVICE_MONITOR_MAC_H_
+
+#include <IOKit/IOKitLib.h>
+
+#include "base/basictypes.h"
+
+namespace content {
+
+class DeviceMonitorMac {
+ public:
+  DeviceMonitorMac();
+  ~DeviceMonitorMac();
+
+ private:
+  void RegisterVideoCallbacks(IONotificationPortRef port);
+  void RegisterAudioCallbacks(IONotificationPortRef port);
+
+  static void VideoDeviceChangedCallback(void *context, io_iterator_t devices);
+  static void AudioDeviceChangedCallback(void *context, io_iterator_t devices);
+
+  void NotifyAudioDeviceChanged();
+  void NotifyVideoDeviceChanged();

[wjia(left Chromium), 2012/08/03 13:50:08]

It seems you can move all these 6 private functions into anonymous namespace in
cc file. This class doesn't have any member anyway.

[no longer working on chromium, 2012/08/03 16:10:15]

Thanks for the ideas. Yes, we can. But then the class becomes hard to be
extended for some other uses who want to use this class for other use cases. For
example, gamepad, they might need to store some members to be able to filter out
the notifications.

I personally prefer this way. Hope it is fine. 

+
+  DISALLOW_COPY_AND_ASSIGN(DeviceMonitorMac);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_DEVICE_MONITOR_MAC_H_