<!DOCTYPE html>

<html>
<head>
    <style>
        .box {
            width: 200px;
            height: 100px;
            background-color: blue;
            margin: 52px 30px;
            position: relative;
            box-shadow: 0 0 10px black;
        }
        
        .dot {
            position: absolute;
            top: 0;
            left: 0;
            height: 4px;
            width: 4px;
            background-color: silver;
        }
        
        body.changed .box {
            animation: move 10s linear;
        }
        
        @keyframes move {
            from {
                -webkit-transform: translatex(10px);
            }
            to {
                -webkit-transform: translatex(100px);
            }
        }
    </style>
    <script>
        if (window.testRunner) {
            testRunner.dumpAsText();
            testRunner.waitUntilDone();
        }

        function dumpLayers()
        {
            if (window.testRunner) {
                document.getElementById('layers').innerText = window.internals.layerTreeAsText(document);
                testRunner.notifyDone();
            }
        }

        function makeDots()
        {
            const width = 40;
            const height = 20;
            
            const spacing = 10;
            
            for (var row = 0; row < height; ++row) {
                for (var col = 0; col < width; ++col) {
                    var dot = document.createElement('div');
                    dot.className = 'dot';
                    dot.style.left = spacing * col + 'px';
                    dot.style.top = spacing * row + 'px';
                    document.body.appendChild(dot);
                }
            }
            
            window.setTimeout(function() {
                document.getElementById('target').addEventListener('animationstart', dumpLayers, false);
                document.body.classList.add('changed');
            }, 0);
        }
        
        window.addEventListener('load', makeDots, false);
    </script>
</head>
<body>

    <div id="target" class="box">
    </div>
<pre id="layers"></pre>
</body>
</html>