timeline-frame.html

Enable keyboard shortcuts

<!DOCTYPE html>

<html>

<head>

  <meta charset="utf-8">

</head>

<script type="text/javascript">

  const targetWindow = window.top.a;

  const element = targetWindow.document.getElementById('target');

  const keyframes = { opacity: [1, 0.2] };

  const options = {

    duration: 1000,

    // Use this document's timeline rather then the timeline of the

    // element's document.

    timeline: document.timeline,

    fill: 'forwards'

};

  element.animate(keyframes, options);

  targetWindow.runTest();

</script>

</html>