<!DOCTYPE html>

<html>
<head>
    <style>
        .box {
            position: absolute;
            top: 10px;
            left: 10px;
            width: 400px;
            height: 400px;
            background-image: url('../resources/alpha-blocks.png');
            background-size: 400px 400px;
        }
        
        #box.moved {
            background-position: -100px -100px;
            top: 110px;
            left: 110px;
        }
        
        .composited {
            -webkit-transform: translateZ(0);
        }
    </style>
    <script>
        if (window.testRunner) {
            testRunner.dumpAsText();
            testRunner.waitUntilDone();
        }

        function test()
        {
            window.setTimeout(function() {
                document.body.offsetTop;
                if (window.internals)
                    window.internals.startTrackingRepaints();

                document.getElementById('box').classList.add('moved');

                if (window.internals)
                    document.getElementById('repaintRects').textContent = window.internals.layerTreeAsText(document, internals.LAYER_TREE_INCLUDES_REPAINT_RECTS);

                if (window.testRunner)
                    testRunner.notifyDone();
            }, 0);
        }
        window.addEventListener('load', test, false);
    </script>
</head>
<body>

    <div id="box" class="composited box"></div>
    <pre id="repaintRects"></pre>
</body>
</html>