<script>
  const channelName = location.search.substr(1),
        channel = new BroadcastChannel(channelName);

  const haveOpener = window.opener !== null;
  const haveReferrer = document.referrer !== null && document.referrer !== "";
  const allBarProps = [
    window.locationbar.visible,
    window.menubar.visible,
    window.personalbar.visible,
    window.scrollbars.visible,
    window.statusbar.visible,
    window.toolbar.visible
  ];
  const isPopup = allBarProps.every(x=>!x);

  channel.postMessage({haveOpener, haveReferrer, isPopup});

  // Because messages are not delivered synchronously and because closing a
  // browsing context prompts the eventual clearing of all task sources, this
  // document should not be closed until the opener document has confirmed
  // receipt.
  channel.onmessage = () => window.close();
</script>
