<html>
<head>
<style>
@font-face {
    font-family: Unused;
    src: url("unused.ttf");
}
@font-face {
    font-family: Used;
    src: url("used.ttf");
}
</style>
</head>
<body onload="fetch('done')">
<span style="font-family: Used">Test</span>
</body>
</html>