Cleaned up the WebRtcAudioCapturer a bit.

content/renderer/media/media_stream_dependency_factory.cc

Index: content/renderer/media/media_stream_dependency_factory.cc
diff --git a/content/renderer/media/media_stream_dependency_factory.cc b/content/renderer/media/media_stream_dependency_factory.cc
index 8d4fe56bdd811ccc2d6f4a1c6a07fbb25044fdb0..500dd0a22a110f9c4e4eb3fc34807a8648833d28 100644
--- a/content/renderer/media/media_stream_dependency_factory.cc
+++ b/content/renderer/media/media_stream_dependency_factory.cc
@@ -305,7 +305,7 @@ void MediaStreamDependencyFactory::CreateNativeMediaSources(
     // source is used in multiple MediaStreams as a result of calling
     // getUserMedia.
     if (source_data->video_source())
-      continue;
+     continue;

[perkj_chrome, 2014/01/12 21:53:06]

indentation

[no longer working on chromium, 2014/01/13 16:59:59]

Done.

 
     const bool is_screencast =
         source_data->device_info().device.type == MEDIA_TAB_VIDEO_CAPTURE ||
@@ -367,7 +367,7 @@ void MediaStreamDependencyFactory::CreateNativeMediaSources(
     }
 
     scoped_refptr<WebRtcAudioCapturer> capturer(
-        MaybeCreateAudioCapturer(render_view_id, device_info));
+        CreateAudioCapturer(render_view_id, device_info));
     if (!capturer.get()) {
       DLOG(WARNING) << "Failed to create the capturer for device "
                     << device_info.device.id;
@@ -455,6 +455,7 @@ MediaStreamDependencyFactory::CreateNativeAudioMediaStreamTrack(
       source_data =
           static_cast<MediaStreamSourceExtraData*>(source.extraData());
     } else {
+      // TODO(xians): Check with perkj on if this comment is valid.

[perkj_chrome, 2014/01/12 21:53:06]

Yes. CreateNativeAudioMediaStreamTrack is called whenever a new track is created
from blink. It can be from a gum call or from cloning a track. 
The the track happen to be a remote track- there is no source object implemented
yet.

[no longer working on chromium, 2014/01/13 16:59:59]

Done with removing the TODO. Good to know, thanks.

       // TODO(perkj): Implement support for sources from
       // remote MediaStreams.
       NOTIMPLEMENTED();
@@ -462,14 +463,9 @@ MediaStreamDependencyFactory::CreateNativeAudioMediaStreamTrack(
     }
   }
 
-  std::string track_id = base::UTF16ToUTF8(track.id());
-  scoped_refptr<WebRtcAudioCapturer> capturer;
-  if (GetWebRtcAudioDevice())
-    capturer = GetWebRtcAudioDevice()->GetDefaultCapturer();
-
   scoped_refptr<webrtc::AudioTrackInterface> audio_track(
-      CreateLocalAudioTrack(track_id,
-                            capturer,
+      CreateLocalAudioTrack(base::UTF16ToUTF8(track.id()),
+                            source_data->GetAudioCapturer(),
                             webaudio_source.get(),
                             source_data->local_audio_source(),
                             &track_constraints));
@@ -930,7 +926,7 @@ void MediaStreamDependencyFactory::CleanupPeerConnectionFactory() {
 }
 
 scoped_refptr<WebRtcAudioCapturer>
-MediaStreamDependencyFactory::MaybeCreateAudioCapturer(
+MediaStreamDependencyFactory::CreateAudioCapturer(
     int render_view_id,
     const StreamDeviceInfo& device_info) {
   // TODO(xians): Handle the cases when gUM is called without a proper render
@@ -938,32 +934,11 @@ MediaStreamDependencyFactory::MaybeCreateAudioCapturer(
   DCHECK_GE(render_view_id, 0);
 
   scoped_refptr<WebRtcAudioCapturer> capturer =
-      GetWebRtcAudioDevice()->GetDefaultCapturer();
-
-  // If the default capturer does not exist or |render_view_id| == -1, create
-  // a new capturer.
-  bool is_new_capturer = false;
-  if (!capturer.get()) {
-    capturer = WebRtcAudioCapturer::CreateCapturer();
-    is_new_capturer = true;
-  }
-
-  if (!capturer->Initialize(
-          render_view_id,
-          static_cast<media::ChannelLayout>(
-              device_info.device.input.channel_layout),
-          device_info.device.input.sample_rate,
-          device_info.device.input.frames_per_buffer,
-          device_info.session_id,
-          device_info.device.id,
-          device_info.device.matched_output.sample_rate,
-          device_info.device.matched_output.frames_per_buffer,
-          device_info.device.input.effects)) {
-    return NULL;
-  }
+      WebRtcAudioCapturer::CreateCapturer(render_view_id, device_info);
 
-  // Add the capturer to the WebRtcAudioDeviceImpl if it is a new capturer.
-  if (is_new_capturer)
+  // Add the capturer to the WebRtcAudioDeviceImpl since it needs some hardware
+  // information from the capturer.
+  if (capturer)

[perkj_chrome, 2014/01/12 21:53:06]

Can capturer be null? 

[no longer working on chromium, 2014/01/13 16:59:59]

Yes, CreateCapturer will return a NULL if it fails to create and initialize the
capturer using the passing |render_view_id| and |device_info|.

     GetWebRtcAudioDevice()->AddAudioCapturer(capturer);

[perkj_chrome, 2014/01/12 21:53:06]

Rename method to SetAudioCapturer if there can be only one? 

[no longer working on chromium, 2014/01/13 16:59:59]

A couple of days ago I landed a workaround to fix a crash when there are
multiple input streams. That means we can actually support multiple capturers,
it is not recommended, but it works. so I don't stop the previous capturers when
a new capturer is created.
AddAudioCapturer() is correct from this sense.

 
   return capturer;