LayoutTests/http/tests/security/resources/loading-subresources.php

<?php
header("Access-Control-Allow-Origin: *");

$name = 'loading-subresources.css';
$fp = fopen($name, 'rb');
header("Content-Type: text/css");
header("Content-Length: " . filesize($name));

fpassthru($fp);
exit;
?>