third_party/blink/web_tests/fast/loader/open-in-srcdoc-unload.html

<iframe id="i"></iframe>
<script>
if (window.testRunner)
    testRunner.dumpAsText();

window.onload = function() {
    document.getElementById("i").srcdoc=">";
}

frames[0].onunload = function () {
    document.open();
    document.close();
};
</script>