<!DOCTYPE html>

<html>
<head>
    <style>
        body {
            background-image: linear-gradient(to top, blue, white);
            height: 5000px;
        }

        body.fixed {
            background-attachment: fixed;
        }

        #layers {
            margin: 100px;
            background-color: silver;
        }
        
        .box {
            height: 100px;
            width: 100px;
            background-color: blue;
        }
        .composited {
            -webkit-transform: translateZ(0);
        }
    </style>
    <script>
        if (window.testRunner) {
            testRunner.dumpAsText();
            testRunner.waitUntilDone();
        }

        function documentLoaded()
        {
            window.setTimeout(doTest, 0);
        }
        
        function doTest()
        {
            document.body.classList.add('fixed');

            if (window.internals)
                document.getElementById('layers').textContent = window.internals.layerTreeAsText(document);
            
            if (window.testRunner)
                testRunner.notifyDone();
        }
        window.addEventListener('load', documentLoaded, false);
    </script>
</head>
<body>

<p>Toggling to a fixed background on the body should make a layer for the background.</p>
<div class="composited box">
    
</div>
<pre id="layers"></pre>

</body>
</html>