LayoutTests/http/tests/loading/form-submission-no-load-event.html

<p>Tests that the load event fires if a form submission to a new window happens during the load.</p>
<div id=log></div>
<form action=about:blank target=_blank><input type=hidden name=input></form>
<script>
  if (window.testRunner) {
    testRunner.dumpAsText();
    testRunner.waitUntilDone();
  }

  timeoutHandle = setTimeout(() => {
    document.querySelector("#log").textContent = `FAIL: The load event did not fire`;
    if (window.testRunner)
      testRunner.notifyDone();
  }, 5000);

  const submitter = document.querySelector("form");
  submitter.submit();

  window.onload = () => {
    document.querySelector("#log").textContent = `PASS: The load event was fired`;
    clearTimeout(timeoutHandle);
    if (window.testRunner)
      testRunner.notifyDone();
  }
</script>