<!DOCTYPE html>

<html>
<head>
    <style>
        .box {
            height: 100px;
            width: 100px;
            margin: 50px;
            background-color: blue;
            box-shadow: 0 0 20px black;
            overflow: hidden;
            -webkit-transform: translateZ(0);
        }
        
        .child {
            position: relative;
            top: -30px;
            left: -30px;
            width: 300px;
            height: 300px;
            background-color: silver;
        }
    </style>
    <script type="text/javascript">
        if (window.testRunner)
            testRunner.dumpAsText();

        function doTest() {
            if (window.testRunner && window.internals)
                document.getElementById('layertree').innerText = window.internals.layerTreeAsText(document);
        }
        window.addEventListener('load', doTest, false);
    </script>
</head>
<body>

    <div class="box">
        <div class="child">
        </div>
    </div>
    <pre id="layertree"></pre> 
</body>
</html>