chromium/third_party/blink/web_tests/compositing/geometry/clipped-video-controller.html

<!DOCTYPE html>

<html>
<head>
  <style>

      #box {
        position: absolute;
        top: 50px;
        left: 20px;
        height: 50px;
        width: 50px;
        overflow: hidden;
        border: 10px solid green;
      }

  </style>
  <script src="../resources/media-testing.js"></script>

  <script type="text/javascript" charset="utf-8">
    if (window.testRunner)
      testRunner.dumpAsText();

    function testDone()
    {
      if (window.testRunner)
        testRunner.notifyDone();
    }

    function doTest()
    {
      var video = document.getElementsByTagName('video')[0];
      setupVideo(video, '../resources/video.ogv', testDone);
    }
  </script>
</head>
<body onload="doTest()">
    <p>The video controller should not be visible below</p>
    <div id="box">
      <video controls></video>
    </div>
</body>
</html>