Handle the case when a mediastream track doesn't have extra data.

content/renderer/media/media_stream_renderer_factory_impl.cc

 // Copyright 2014 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_stream_renderer_factory_impl.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "content/renderer/media/media_stream.h"
 #include "content/renderer/media/media_stream_video_renderer_sink.h"
 #include "content/renderer/media/media_stream_video_track.h"
@@ skipping 123 matching lines @@
   DVLOG(1) << "MediaStreamRendererFactoryImpl::GetAudioRenderer stream:"
            << base::UTF16ToUTF8(base::StringPiece16(web_stream.id()));
 
   // TODO(tommi): We need to fix the data flow so that
   // it works the same way for all track implementations, local, remote or what
   // have you.
   // In this function, we should simply create a renderer object that receives
   // and mixes audio from all the tracks that belong to the media stream.
   // For now, we have separate renderers depending on if the first audio track
   // in the stream is local or remote.
-  if (MediaStreamTrack::GetTrack(audio_tracks[0])->is_local_track()) {
+  MediaStreamTrack* audio_track = MediaStreamTrack::GetTrack(audio_tracks[0]);
+  if (!audio_track) {
+    // This can happen if the track was cloned.
+    // TODO(tommi, perkj): Fix cloning of tracks to handle extra data too.

[perkj_chrome, 2015/12/10 12:44:44]

Is this an audio track problem in general or only webaudio? 

Cloning is triggered from here:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

And implemented in chrome here.
https://code.google.com/p/chromium/codesearch#chromium/src/content/renderer/m...

[tommi (sloooow) - chröme, 2015/12/10 13:37:37]

In general and I don't think this is an issue with webaudio tracks actually.
Yes I know and the problem with that implementation is that the extra data is
not cloned and there's no way to get to the original source of the original
track.  For remote tracks for example, there will never be a "native" source or
track.

+    LOG(ERROR) << "No native track for WebMediaStreamTrack.";
+    return nullptr;
+  }
+
+  if (audio_track->is_local_track()) {
     // TODO(xians): Add support for the case where the media stream contains
     // multiple audio tracks.
     return CreateLocalAudioRenderer(audio_tracks[0], render_frame_id, device_id,
                                     security_origin);
   }
 
   // This is a remote WebRTC media stream.
   WebRtcAudioDeviceImpl* audio_device =
       GetPeerConnectionDependencyFactory()->GetWebRtcAudioDevice();
 
   // Share the existing renderer if any, otherwise create a new one.
   scoped_refptr<WebRtcAudioRenderer> renderer(audio_device->renderer());
   if (!renderer.get()) {
     renderer = CreateRemoteAudioRenderer(web_stream, render_frame_id,
                                          device_id, security_origin);
 
     if (renderer.get() && !audio_device->SetAudioRenderer(renderer.get()))
       renderer = NULL;
   }
 
   return renderer.get() ? renderer->CreateSharedAudioRendererProxy(web_stream)
                         : NULL;
 }
 
 }  // namespace content