Implement MediaCaptureDevices.

content/public/browser/media_capture_devices.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_PUBLIC_BROWSER_MEDIA_CAPTURE_DEVICES_H_
+#define CONTENT_PUBLIC_BROWSER_MEDIA_CAPTURE_DEVICES_H_
+
+#include "content/public/common/media_stream_request.h"
+
+namespace content {
+
+// This is a singleton class, used to get Audio/Video devices.

[Sergey Ulanov, 2014/03/06 08:26:40]

Please mention that it must be used on the UI thread.

[michaelbai, 2014/03/06 19:27:20]

Done.

+CONTENT_EXPORT class MediaCaptureDevices {

[Sergey Ulanov, 2014/03/06 08:26:40]

CONTENT_EXPORT should be between 'class' and the class name.

[Sergey Ulanov, 2014/03/06 08:26:40]

Does this class need to be be a singleton? E.g. can it be stored in
MediaStreamManager? If not, them maybe rename it to make it clear it's a
singleton, e.g. MediaCaptureDevicesCache.

[michaelbai, 2014/03/06 19:27:20]

Done.

[michaelbai, 2014/03/06 19:27:20]

MediaStreamManager is not content API, browser can't access MediaCaptureDevices
from it; To make a singletone is reasonable, it has all devices information of a
system, and shouldn't have second instance, I think MediaCaptureDevices is also
a good name, this class do have a list of devices. 

On 2014/03/06 08:26:40, Sergey Ulanov wrote:

+ public:
+  // Get signleton instance of MediaCaptureDevices.
+  static MediaCaptureDevices* GetInstance();
+
+  // Return all Audio/Video devices.
+  virtual const MediaStreamDevices& GetAudioCaptureDevices() = 0;
+  virtual const MediaStreamDevices& GetVideoCaptureDevices() = 0;
+
+ private:
+  // This interface should only be implemented inside content.
+  friend class MediaCaptureDevicesImpl;
+  MediaCaptureDevices() {}
+  virtual ~MediaCaptureDevices() {}
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_MEDIA_CAPTURE_DEVICES_H_