chromium/third_party/blink/web_tests/external/wpt/html/cross-origin-opener-policy/resources/resource-popup.html

<!DOCTYPE html>
<html lang="en">
<meta charset="utf-8">
<title></title>
<script>
'use strict';
const params = new URL(location).searchParams;
const bc = new BroadcastChannel(params.get('channel_name'));
const win = open(params.get('resource'), params.get('resource_name'));

bc.onmessage = () => {
  win.close();
  close();
};
const id = setInterval(() => {
  if (win.closed || win.location.href !== 'about:blank') {
    clearInterval(id);
    const winName = (() => {
      try {
        return win.name;
      } catch (e) {
        return null;
      }
    })();
    bc.postMessage({name: winName || null, closed: win.closed});
  }
}, 100);
</script>