<script>
  if (window.testRunner) 
    testRunner.dumpAsText();
  internals.useMockRTCPeerConnectionFactory('');
  let track = new AudioContext().createMediaStreamDestination().stream.getAudioTracks()[0];
  new RTCPeerConnection().addTrack(track).dtmf;
</script>
<body>This test passes if it doesn't crash.</body>
