Cleaned up the WebRtcAudioCapturer a bit.

content/renderer/media/rtc_peer_connection_handler.cc

Index: content/renderer/media/rtc_peer_connection_handler.cc
diff --git a/content/renderer/media/rtc_peer_connection_handler.cc b/content/renderer/media/rtc_peer_connection_handler.cc
index 08f71c064b371d3c20beba4ae47d339b8d7c67a9..6548faa66b774fd724dea55adbe64d0303b7ee7a 100644
--- a/content/renderer/media/rtc_peer_connection_handler.cc
+++ b/content/renderer/media/rtc_peer_connection_handler.cc
@@ -15,6 +15,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "content/public/common/content_switches.h"
 #include "content/renderer/media/media_stream_dependency_factory.h"
+#include "content/renderer/media/media_stream_source_extra_data.h"
 #include "content/renderer/media/peer_connection_tracker.h"
 #include "content/renderer/media/remote_media_stream_impl.h"
 #include "content/renderer/media/rtc_data_channel_handler.h"
@@ -549,13 +550,16 @@ bool RTCPeerConnectionHandler::addStream(
         this, stream, PeerConnectionTracker::SOURCE_LOCAL);
 
   // A media stream is connected to a peer connection, enable the
-  // peer connection mode for the capturer.
-  WebRtcAudioDeviceImpl* audio_device =
-      dependency_factory_->GetWebRtcAudioDevice();
-  if (audio_device) {
-    WebRtcAudioCapturer* capturer = audio_device->GetDefaultCapturer();
-    if (capturer)
-      capturer->EnablePeerConnectionMode();
+  // peer connection mode for the sources.
+  blink::WebVector<blink::WebMediaStreamTrack> audio_tracks;
+  stream.audioTracks(audio_tracks);
+  for (size_t i = 0; i < audio_tracks.size(); ++i) {
+    const blink::WebMediaStreamSource& source = audio_tracks[i].source();
+    MediaStreamSourceExtraData* extra_data =
+        static_cast<MediaStreamSourceExtraData*>(source.extraData());
+    // |extra_data| is NULL if the track is a remote audio track.
+    if (extra_data && extra_data->GetAudioCapturer())
+      extra_data->GetAudioCapturer()->EnablePeerConnectionMode();
   }
 
   return AddStream(stream, &constraints);