LayoutTests/http/tests/security/mixedContent/resources/frame-with-redirect-https-to-http-frame.html

<script>
var frameDidLoad = false;

onload = function()
{
    if (window.opener)
        window.opener.postMessage(frameDidLoad ? 'done' : 'blocked', '*');
}

</script>
<iframe onload="window.frameDidLoad = true"
        src="https://127.0.0.1:8443/resources/redirect.php?url=http://127.0.0.1:8080/security/mixedContent/resources/boring.html"></iframe>