<!DOCTYPE html>

<html>
<head>
    <style>
        body {
            margin: 0;
        }

        #scroller {
            margin: 10px;
            height: 300px;
            width: 300px;
            background-color: green;
            overflow-y: scroll;
        }
        
        .contents {
            width: 100%;
            height: 200%;
            background-color: silver;
        }

        .scrollbar-hider {
            position: absolute;
            top: 10px;
            left: 294px;
            width: 16px;
            height: 300px;
            background-color: gray;
        }
    </style>
    <script>
        if (window.internals)
            internals.setUsesOverlayScrollbars(true);

        function doTest()
        {
            var scroller = document.getElementById('scroller');
            if (window.internals)
                internals.unconstrainedScrollTo(scroller, 0, -150);
        }
        
        window.addEventListener('load', doTest, false);
    </script>
</head>
<body>

<div id="scroller">
    <div class="contents"></div>
</div>
<div class="scrollbar-hider"></div>
</body>
</html>