http/tests/security/resources/referrer-policy-postmessage.php

<html>
<head>
<script>
function log(msg) {
    window.opener.postMessage(msg, "*");
}

function runTest() {
    var referrerHeader = "<?php echo $_SERVER['HTTP_REFERER'] ?>";
    if (referrerHeader == "")
        log("HTTP Referer header is empty");
    else
        log("HTTP Referer header is " + referrerHeader);

    if (document.referrer == "")
        log("Referrer is empty");
    else
        log("Referrer is " + document.referrer);

    log("done");
}
</script>
</head>
<body onload="runTest()">
</body>
</html>