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chromium/third_party/blink/web_tests/http/tests/navigation/resources/form-submit-from-opened-window-helper.html 

<html>
<body>
<form name="input" action="pass-and-notify-done.html" method="post"target="start"></form>
<script>
window.onload = function() {
    document.forms[0].submit();
    window.close();
}
</script>
</body>
</html>