start/stop the source of the capturer when 1st audiotrack/last audiotrack is added/removed

content/renderer/media/webrtc_local_audio_track.cc

Index: content/renderer/media/webrtc_local_audio_track.cc
diff --git a/content/renderer/media/webrtc_local_audio_track.cc b/content/renderer/media/webrtc_local_audio_track.cc
index 0aa63658c516256a90b33696437143d775199f2b..4abd407f28afc8c9409f3eb23725434658183485 100644
--- a/content/renderer/media/webrtc_local_audio_track.cc
+++ b/content/renderer/media/webrtc_local_audio_track.cc
@@ -29,14 +29,13 @@ WebRtcLocalAudioTrack::WebRtcLocalAudioTrack(
       capturer_(capturer),
       track_source_(track_source) {
   DCHECK(capturer.get());
-  capturer_->AddSink(this);
   DVLOG(1) << "WebRtcLocalAudioTrack::WebRtcLocalAudioTrack()";
 }
 
 WebRtcLocalAudioTrack::~WebRtcLocalAudioTrack() {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(sinks_.empty());
-  capturer_->RemoveSink(this);
+  DCHECK(!capturer_.get());

[henrika (OOO until Aug 14), 2013/06/05 09:09:20]

What ensures that RemoveSink i called now?

[no longer working on chromium, 2013/06/05 16:29:45]

Right, I also realized it this morning, we should handle it instead of using a
DCHECK here.

   DVLOG(1) << "WebRtcLocalAudioTrack::~WebRtcLocalAudioTrack()";
 }
 
@@ -124,4 +123,17 @@ void WebRtcLocalAudioTrack::RemoveSink(
   }
 }
 
+void WebRtcLocalAudioTrack::Start() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DVLOG(1) << "WebRtcLocalAudioTrack::Start()";
+  capturer_->AddSink(this);
+}
+
+void WebRtcLocalAudioTrack::Stop() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DVLOG(1) << "WebRtcLocalAudioTrack::Stop()";
+  capturer_->RemoveSink(this);
+  capturer_ = NULL;
+}
+
 }  // namespace content