chromium/src/third_party/blink/web_tests/http/tests/serviceworker/resources/fetch-access-control-login.html

<script>
// Set authentication info
window.addEventListener("message", function(evt) {
    var port = evt.ports[0];
    // Cookies intended for cross-site use must be marked SameSite=None and Secure.
    document.cookie = 'cookie=' + evt.data.cookie + (evt.data.cookieCrossSite ? "; SameSite=None; Secure" : "");
    var xhr = new XMLHttpRequest();
    xhr.addEventListener('load', function() {
        port.postMessage({msg: 'LOGIN FINISHED'});
      }, false);
    xhr.open('GET',
             './fetch-access-control.php?Auth',
             true,
             evt.data.username, evt.data.password);
    xhr.send();
  }, false);
</script>