chromium/third_party/blink/web_tests/external/wpt/html/browsers/windows/auxiliary-browsing-contexts/resources/message-window-opener.html

<script src="/common/PrefixedLocalStorage.js"></script>
<script>
var prefixedLocalStorage = new PrefixedLocalStorageResource({
  close_on_cleanup: true
});

if (window.opener) {
  window.opener.postMessage ({
    name      : window.name,
    openerName: window.opener.name,
    isTop     : window.top === window
  }, '*');
}
</script>