LayoutTests/webanimations/opacity-animation-yields-compositing.html

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

document.getElementById("target").animate([
    { opacity: 1 },
    { opacity: 0 }
], 1000);

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

</script>