<!DOCTYPE html>
<html>
<head>
<style>

#target {
    width: 100px;
    height: 100px;
    background-color: black;
}

</style>
</head>
<body>
<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>
<div id="target"></div>
<script>

function waitNFrames(numberOfFrames, continuation)
{
    let elapsedFrames = 0;
    (function rAFCallback() {
        if (elapsedFrames++ >= numberOfFrames)
            continuation();
        else
            requestAnimationFrame(rAFCallback);
    })();
}

async_test(t => {
    const keyframes = { transform: ["translateX(50px)", "translateX(100px)"] };
    const timing = { duration: 50, fill: "forwards" };
    document.getElementById("target").animate(keyframes, timing).addEventListener("finish", event => {
        const numberOfTimelineInvalidationsWhenFinished = internals.numberOfAnimationTimelineInvalidations();
        waitNFrames(3, () => {
            assert_equals(internals.numberOfAnimationTimelineInvalidations(), numberOfTimelineInvalidationsWhenFinished + 1);
            t.done();
        });
    });
}, "There should not be more than one update made to the timeline after a forward-filling accelerated animation completes.");

</script>
</body>
</html>