mozilla-release/testing/web-platform/tests/feature-policy/feature-policy-frame-policy-timing-iframe-camera.https.sub.html

<!DOCTYPE html>
<meta charset="utf-8">
<script>
window.onmessage = m => {
  navigator.mediaDevices.getUserMedia({video: true})
    .then(() => 'ok')
    .catch(e => e.name)
    .then(r => {
      window.parent.postMessage({
        id: m.data.id,
        result: r
      }, '*');
    });
}
</script>