LayoutTests/webanimations/opacity-animation-no-longer-composited-upon-completion.html

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

const animation = new Animation(new KeyframeEffect(document.getElementById("target"), [
    { opacity: 1 },
    { opacity: 0 }
]));
animation.startTime = 0;
animation.effect.timing.duration = 100;

testRunner.waitUntilDone();
testRunner.dumpAsText();

setTimeout(() => {
    document.getElementById("results").innerText = internals.layerTreeAsText(document);
    testRunner.notifyDone();
}, animation.effect.timing.duration + 500);

</script>