LayoutTests/http/tests/security/resources/credentials-iframes-continued.html

<script>
window.addEventListener("message", function(event) {
    alert("parent host: " + window.location.hostname + event.data);
    if (window.testRunner)
        testRunner.notifyDone();
}, false);
</script>
<iframe src="http://127.0.0.1:8000/security/resources/credentials-iframes-different-domain.html"></iframe>