chromium/third_party/blink/web_tests/http/tests/loading/onbeforeunload-detach.html

<script>
if (window.testRunner) {
  testRunner.dumpAsText();
  testRunner.waitUntilDone();
}

function iframeDone() {
  console.log('main frame: iframe is done');
  setTimeout(() => {
    if (window.testRunner)
      testRunner.notifyDone();
  }, 0);
}
</script>
<iframe name="iframe" src="resources/onbeforeunload-detach-iframe.html"></iframe>
This test passes if it does not crash.