chromium/third_party/blink/web_tests/external/wpt/fedcm/support/fedcm-iframe-level2.html

<!doctype html>
<link rel="help" href="https://wicg.github.io/FedCM">
<script src="/common/get-host-info.sub.js"></script>
<div id=log>
<script>
'use strict';

const host = get_host_info();
const remoteBaseURL =
    host.AUTHENTICATED_ORIGIN +
    window.location.pathname.replace(/\/[^\/]*$/, '/');

window.onload = async () => {
  const urlParams = new URLSearchParams(window.location.search);
  var iframe = document.createElement("iframe");
  iframe.src = remoteBaseURL + "fedcm-iframe.html";
  if (urlParams.get("permission") != '0') {
    iframe.allow = "identity-credentials-get";
  }
  document.body.appendChild(iframe);
};

</script>