<html>
<head>
<script>
window.addEventListener('load', async () => {
  const frame = document.createElement('frame')
  document.documentElement.appendChild(frame)
  const pc = new RTCPeerConnection({})
  await pc.createOffer({ 'offerToReceiveAudio': true })
  const [{receiver}] = pc.getTransceivers()
  const track = pc.addTrack(receiver.track)
  pc.removeTrack(track)
  const [track2] = (await frame.contentWindow.navigator.mediaDevices.getUserMedia({
    'audio': {},
    'fake': true
  })).getTracks()
  pc.addTrack(track2)
})
</script>
</head>
</html>
