<!DOCTYPE html>

<html>
<head>
    <style>
        .bar {
            width: 200px;
            height: 50px;
            margin-left: 50px;
            background-color: gray;
            -webkit-transform: translateZ(0);
        }

        #overflow {
            position: absolute;
            top: 70px;
            left: 100px;
            z-index: 100;
            height: 200px;
            width: 200px;
            border: 1px solid black;
            overflow: scroll;
        }
        
        #overflow > div {
            position: relative;
            height: 50px;
            width: 100%;
            border: 2px solid black;
            margin: 2px;
        }
        
    </style>
    <script>
        if (window.testRunner) {
            testRunner.dumpAsText(true);
            testRunner.waitUntilDone();
        }

        function doTest()
        {
            var overflow = document.getElementById('overflow');
            overflow.scrollTop = 50;

            if (window.testRunner)
                testRunner.displayAndTrackRepaints();
            
            window.setTimeout(function() {
                overflow.scrollTop = 75;
                if (window.testRunner)
                    testRunner.notifyDone();
            }, 0)
        }
        window.addEventListener('load', doTest, false);
    </script>
</head>
<body>

    <div class="bar"></div>
    
    <div id="overflow">
        <div></div>
        <div></div>
        <div></div>
        <div></div>
        <div></div>
    </div>
</body>
</html>