<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 [{sender, receiver}] = pc.getTransceivers()
  await sender.replaceTrack(receiver.track)
  await sender.replaceTrack(null)
  const stream = await frame.contentWindow.navigator.mediaDevices.getUserMedia({
    'audio': {},
    'fake': true
  })
  await sender.replaceTrack(stream.getTracks()[0])
})
</script>
</head>
</html>
