transition-ends-before-animation-frame.html

<!DOCTYPE html>
<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>
<script src="../resources/gesture-util.js"></script>
<body>
<script>

window.onload = async () => {
  document.timeline.playbackRate = 0;
  document.timeline.currentTime = 0;

  async function waitForTransitionEnd() {
    return new Promise(resolve => {
      window.ontransitionend = resolve;
    });
  }

  promise_test(async t => {
    await waitForCompositorCommit();
    const transitionPromise = waitForTransitionEnd();
    document.body.style.transition = 'background 100ms';
    document.body.style.background = 'green';
    setTimeout(function() {
      document.timeline.currentTime = 100;
      document.body.offsetTop; // Forces a style recalc, on-demand timing update.
    });
    await transitionPromise;
  }, 'Transition end event should fire even if it completes in an on-demand ' +
     'timing update');
};
</script>

chromium/third_party/blink/web_tests/transitions/transition-ends-before-animation-frame.html