LayoutTests/webanimations/width-and-opacity-separate-animation-yields-compositing.html

<pre id="results"></pre>
<div id="target" style="width: 100px; height: 100px; background-color: black;"></div>
<script>

target.animate([
    { opacity: 1, width: "100px" },
    { opacity: 0, width: "200px" }
], 1000);

testRunner.dumpAsText();
document.getElementById("results").innerText = internals.layerTreeAsText(document);

</script>