LayoutTests/webanimations/accelerated-translate-animation-underlying-transform-changed-in-flight.html

<style>

    #target {
        position: absolute;
        top: 0;
        left: 0;
        width: 100px;
        height: 100px;
        background-color: black;
    }

</style>
<div id="target"></div>
<script src="../resources/ui-helper.js"></script>
<script>

(async () => {
    if (window.testRunner)
        testRunner.waitUntilDone();

    // Start an animation that lasts a day.
    const duration = 24 * 60 * 60 * 1000;
    const target = document.getElementById("target");
    const animation = target.animate({ translate: "200px" }, duration);
    animation.currentTime = duration / 2;

    // Wait until the animation has been applied.
    await animation.ready;
    await UIHelper.ensureStablePresentationUpdate();

    // Change the transform property.
    target.style.transform = "translateY(100px)";

    // Wait until that change was made.
    await UIHelper.ensureStablePresentationUpdate();

    if (window.testRunner)
        testRunner.notifyDone();
})();

</script>