chromium/third_party/blink/web_tests/external/wpt/workers/support/window-sw-shared-name.html

<!DOCTYPE html>
<title>Window for cross-origin iframe with Shared Worker</title>
<script src="/common/get-host-info.sub.js"></script>

<body>
<script>

const iframe_url = new URL(
  'iframe-sw-shared-name.html',
    get_host_info().ORIGIN + self.location.pathname);


window.onmessage = (e) => {window.opener.postMessage(e.data, '*')};

var frame = document.createElement('iframe');
frame.src = iframe_url;
frame.style.position = 'absolute';
document.body.appendChild(frame);

</script>
</body>
</html>