chromium/components/test/data/subresource_filter/iframe_spoof_click_popup.html

<iframe src="window_open_spoof_click.html"></iframe>
<script>
function openWindow() {
  var iframe = document.getElementsByTagName('iframe')[0];
  return new Promise(resolve => {
    window.addEventListener('message', function() {
      resolve(true);
    });
    iframe.contentWindow.postMessage('', self.origin);
  });
}

</script>