chromium/third_party/blink/web_tests/fast/css/fontfaceset-in-detached-frame.html

<html>
<head>
<script src="../../resources/js-test.js"></script>
</head>
<body>
<script>
description('Call FontFaceSet::ready in a detached frame.');

if (window.testRunner)
    testRunner.dumpAsText();

function runTests() {
    var frame = document.createElement('iframe');
    document.body.appendChild(frame);
    var doc = frame.contentDocument;
    document.body.removeChild(frame);
    doc.fonts.ready;
}

if (document.fonts) {
    runTests();
} else {
    testFailed('document.fonts does not exist');
}
</script>
</body>
</html>