Set audio format before adding pepper sink to audio track.

content/public/renderer/media_stream_audio_sink.cc

Index: content/public/renderer/media_stream_audio_sink.cc
diff --git a/content/public/renderer/media_stream_audio_sink.cc b/content/public/renderer/media_stream_audio_sink.cc
index 5b14f95b4f254c09a5b98c95811fc7f8695ddb52..507bef0fa29c9e6cdb623e5fbc7f7ce8d497cc3f 100644
--- a/content/public/renderer/media_stream_audio_sink.cc
+++ b/content/public/renderer/media_stream_audio_sink.cc
@@ -43,4 +43,17 @@ void MediaStreamAudioSink::RemoveFromAudioTrack(
   audio_track->RemoveSink(sink);
 }
 
+media::AudioParameters MediaStreamAudioSink::GetFormatFromAudioTrack(
+    const blink::WebMediaStreamTrack& track) {
+  MediaStreamTrack* native_track = MediaStreamTrack::GetTrack(track);
+  if (!native_track->is_local_track()) {
+    LOG(ERROR) << "Can't get format from a remote audio track";
+    return media::AudioParameters();
+  }
+
+  WebRtcLocalAudioTrack* audio_track =
+      static_cast<WebRtcLocalAudioTrack*>(native_track);
+  return audio_track->GetOutputFormat();
+}
+
 }  // namespace content