Set audio format before adding pepper sink to audio track.

content/renderer/media/webrtc_audio_capturer.h

Index: content/renderer/media/webrtc_audio_capturer.h
diff --git a/content/renderer/media/webrtc_audio_capturer.h b/content/renderer/media/webrtc_audio_capturer.h
index b8aae22c4f094ff5594ef61d648a210566790efd..ed72fad14ac9eeb687505da24c89deb9ae925e6c 100644
--- a/content/renderer/media/webrtc_audio_capturer.h
+++ b/content/renderer/media/webrtc_audio_capturer.h
@@ -105,6 +105,10 @@ class CONTENT_EXPORT WebRtcAudioCapturer
   // call Stop()
   void Stop();
 
+  // Returns the output format.
+  // Called on the main render thread.
+  media::AudioParameters GetOutputFormat() const;
+
   // Used by the unittests to inject their own source to the capturer.
   void SetCapturerSourceForTesting(
       const scoped_refptr<media::AudioCapturerSource>& source,