Set audio format before adding pepper sink to audio track.

content/renderer/media/webrtc_audio_capturer.cc

Index: content/renderer/media/webrtc_audio_capturer.cc
diff --git a/content/renderer/media/webrtc_audio_capturer.cc b/content/renderer/media/webrtc_audio_capturer.cc
index 0765c00d4d0c59251d5bed94646e8ef008d51024..dc58cc74592603d2d3e424c774a9ad16908b9289 100644
--- a/content/renderer/media/webrtc_audio_capturer.cc
+++ b/content/renderer/media/webrtc_audio_capturer.cc
@@ -434,6 +434,11 @@ int WebRtcAudioCapturer::MaxVolume() const {
   return WebRtcAudioDeviceImpl::kMaxVolumeLevel;
 }
 
+const media::AudioParameters& WebRtcAudioCapturer::GetOutputFormat() const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return audio_processor_->OutputFormat();
+}
+
 void WebRtcAudioCapturer::Capture(const media::AudioBus* audio_source,
                                   int audio_delay_milliseconds,
                                   double volume,