<!DOCTYPE html>
<html>
<head>
    <style>
        #caption {
            width: 200px;
            height: 100px;
            background-color: green;
            will-change: transform;
        }
        .inner {
            visibility: visible;
            background-color: blue;
        }
    </style>
    <script type="text/javascript">
        if (window.testRunner)
            testRunner.dumpAsText();

        function doTest() {
            document.getElementById("caption").style.visibility = "hidden";
            if (window.testRunner && window.internals)
                document.getElementById('layertree').innerText = internals.layerTreeAsText(document);
        }
        window.addEventListener('load', doTest, false);
    </script>
</head>
<body>
    <div id="caption" style="position: fixed; background: green;">
      <span class="inner">Caption</span></div>
<pre id="layertree"></pre>
</body>
</html>