<script>
function testSameOrigin()
{
    var req = new XMLHttpRequest;
    req.open("GET", "xhr-vary-header-response.php");
    req.onload=function() { parent.postMessage(req.responseText, "http://127.0.0.1:8000") }
    req.send();
}

window.onmessage = function() { testSameOrigin() }
</script>

<button onclick="testSameOrigin()">Make same origin request</button>