This allow connection remote stream to audio tag, and enable users to control the audio via audio tag controller.

      Since WebRtcAudioDeviceImpl is not a thread safe class, it can only take commands from VoE, so the output code (including AudioOutputDevice) is broken down into a WebRtcAudioRenderer. This WebRtcAudioRenderer gets calls from 3 threads:
WebRtcAudioDeviceImpl thread for commands: Play(), Pause()
WebMediaPlayer thread for commands: Play(), Pause(), Stop(), SetVolume()
Audio thread: Render() callback.


BUG=142988
TEST=https://webrtc-demos.appspot.com/html/pc1.html, make a call, right click to show the controller, you should be able to control the audio in the second tag.

Review URL: https://chromiumcodereview.appspot.com/11270012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@164814 0039d316-1c4b-4281-b951-d872f2087c98