<iframe id=iframe></iframe>
<script>
if (window.testRunner) {
    testRunner.waitUntilDone();
    testRunner.dumpAsText();
}

iframe.srcdoc = `<script>onbeforeunload = async () => {
    await clientInformation.storage.persist();
    document.designMode = 'off';
    document.title = 'x';
};</scri`+`pt>`;
iframe.onload = () => {
    iframe.onload = () => {
        if (window.testRunner)
            testRunner.notifyDone();
    };
    iframe.srcdoc = "foo";
};
</script>
This test passes if it doesn't crash.