navigation-unload-form-submit-1.html

<!DOCTYPE html>

<h1>navigation-unload-form-submit-1.html</h1>

<script>
let isSubmit = false;

window.unload = function () {
    window.location = 'is-Submit' + isSubmit;
}

function setIsSubmit() {
    isSubmit = true;
}
</script>

<form onsubmit="setIsSubmit" action="navigation-unload-form-submit-2.html">
  <input type="submit">
</form>

<script>
parent.finishedLoading();
</script>

chromium/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/navigating-across-documents/navigation-unload-form-submit-1.html