LayoutTests/http/tests/security/css-mask-image-credentials.html

<script>
    if (window.testRunner) { testRunner.waitUntilDone() }
    
    function reqListener () {
      window.location.href = "resources/css-mask-image-credentials-2.html";
    }

    var oReq = new XMLHttpRequest();
    oReq.addEventListener("load", reqListener);
    oReq.open("GET", "http://testusername:testpassword@127.0.0.1:8000/security/resources/image-credential-check.py");
    oReq.send();
</script>