mozilla-release/layout/reftests/bugs/1358375-3.html

<!DOCTYPE html>
<html class="reftest-wait">
  <head>
    <style>
#x { }
#x { color: green; }
    </style>
  </head>
  <body onload="getComputedStyle(document.getElementById('x')).color;
                document.styleSheets[0].cssRules[0].style.setProperty('color', 'orange', 'important');
                document.documentElement.removeAttribute('class');">
    <div id="x"><span>I should be orange</span></div>
  </body>
</html>