Implement MediaCaptureDevices.

content/browser/renderer_host/media/media_capture_devices_impl.h

+// Copyright 2014 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_RENDERER_HOST_MEDIA_MEDIA_CAPTURE_DEVICES_H
+#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_CAPTURE_DEVICES_H
+
+#include "base/memory/singleton.h"
+#include "content/public/browser/media_capture_devices.h"
+
+namespace content {
+
+class MediaCaptureDevicesImpl : public MediaCaptureDevices {
+ public:
+  static MediaCaptureDevicesImpl* GetInstance();
+
+  // Overriden from MediaCaptureDevices
+  virtual const MediaStreamDevices& GetAudioCaptureDevices() OVERRIDE;
+  virtual const MediaStreamDevices& GetVideoCaptureDevices() OVERRIDE;
+
+  // Called by MediaStreamManager to notify the change of media capture
+  // devices, these 2 methods are called in IO thread.
+  void OnAudioCaptureDevicesChanged(const MediaStreamDevices& devices);
+  void OnVideoCaptureDevicesChanged(const MediaStreamDevices& devices);
+
+ private:
+  friend struct DefaultSingletonTraits<MediaCaptureDevicesImpl>;
+  MediaCaptureDevicesImpl();
+  virtual ~MediaCaptureDevicesImpl();
+
+  // Called by the MediaObserver() functions, executed on UI thread.

[wjia(left Chromium), 2014/03/07 04:32:43]

This comment doesn't match the context here.

[michaelbai, 2014/03/07 06:59:31]

Done.

+  void UpdateAudioDevicesOnUIThread(const content::MediaStreamDevices& devices);
+  void UpdateVideoDevicesOnUIThread(const content::MediaStreamDevices& devices);
+
+  // Flag to indicate if device enumeration has been done/doing.
+  // Only accessed on UI thread.
+  bool devices_enumerated_;
+
+  // A list of cached audio capture devices.
+  MediaStreamDevices audio_devices_;
+
+  // A list of cached video capture devices.
+  MediaStreamDevices video_devices_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaCaptureDevicesImpl);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_CAPTURE_DEVICES_H