LayoutTests/http/tests/misc/multiple-submit.html

<form name=f action='resources/post-echo-and-notify-done.cgi' method=post>
<input id=sub type=submit onclick='return clickf();'>
<input id=val type=hidden name=submitted value='form1'>
</form>

<form name=f2 action='resources/post-echo-and-notify-done.cgi' method=post>
<input id=val type=hidden name=submitted value='form2'>
</form>

<script>
function clickf()
{
    document.f2.submit();
    return true;
}

if (window.testRunner) {
    testRunner.waitUntilDone();
    testRunner.dumpAsText();
}

setTimeout(function() { document.getElementById('sub').click(); }, 0);
</script>