chromium/third_party/blink/web_tests/fast/css/nested-rule-parent-sheet.html

<html>
<head>
<style>
@media screen {
  @font-face {
    src: local('Courier');
    font-family: Courier;
  }
}
</style>
<body>
<div id="console"></div>

<script>
if (window.testRunner)
    testRunner.dumpAsText();

function log(message)
{
    var console = document.getElementById("console");
    console.appendChild(document.createTextNode(message + "\n"));
}

log("The parent sheet of a font face rule inside a media block should be defined: " + document.styleSheets[0].cssRules[0].cssRules[0].parentStyleSheet);
</script>