Update WebmMuxer for audio component of MediaStream recording.

content/renderer/media/media_recorder_handler.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/media/media_recorder_handler.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "content/renderer/media/video_track_recorder.h"
@@ skipping 62 matching lines @@
 bool MediaRecorderHandler::start(int timeslice) {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   DCHECK(!recording_);
   DCHECK(!media_stream_.isNull());
   DCHECK(!webm_muxer_);
   DCHECK(timeslice_.is_zero());
 
   timeslice_ = TimeDelta::FromMilliseconds(timeslice);
   slice_origin_timestamp_ = TimeTicks::Now();
 
-  webm_muxer_.reset(
-      new media::WebmMuxer(use_vp9_ ? media::kCodecVP9 : media::kCodecVP8,
-                           base::Bind(&MediaRecorderHandler::WriteData,
-                                      weak_factory_.GetWeakPtr())));
-
   blink::WebVector<blink::WebMediaStreamTrack> video_tracks;
   media_stream_.videoTracks(video_tracks);
 
+  webm_muxer_.reset(
+      new media::WebmMuxer(use_vp9_ ? media::kCodecVP9 : media::kCodecVP8,
+                           video_tracks.size(), 0 /* no audio for now */,
+                           base::Bind(&MediaRecorderHandler::WriteData,
+                                      weak_factory_.GetWeakPtr())));
+
   if (video_tracks.isEmpty()) {
     // TODO(mcasas): Add audio_tracks and update the code in this function
     // correspondingly, see http://crbug.com/528519. As of now, only video
     // tracks are supported.
     LOG(WARNING) << "Recording no video tracks is not implemented";
     return false;
   }
   // TODO(mcasas): The muxer API supports only one video track. Extend it to
   // several video tracks, see http://crbug.com/528523.
   LOG_IF(WARNING, video_tracks.size() > 1u) << "Recording multiple video"
@@ skipping 70 matching lines @@
 }
 
 void MediaRecorderHandler::OnVideoFrameForTesting(
     const scoped_refptr<media::VideoFrame>& frame,
     const TimeTicks& timestamp) {
   for (auto* recorder : video_recorders_)
     recorder->OnVideoFrameForTesting(frame, timestamp);
 }
 
 }  // namespace content