chromium/chrome/test/data/media/picture-in-picture/autopip-document.html

<!DOCTYPE html>
<head>
<meta charset="utf-8">
<title>Autopip Document Picture-in-Picture</title>
</head>
<body>
  <video id="video" controls loop>
    <source src="../bigbuck.webm">
  </video>
</body>
<script>
const video = document.getElementById('video');

function playVideo() {
  navigator.mediaSession.playbackState = "playing";
  video.play();
}

function pauseVideo() {
  video.pause();
  navigator.mediaSession.playbackState = "paused";
}

function openPip() {
  documentPictureInPicture.requestWindow();
}

navigator.mediaSession.setActionHandler('enterpictureinpicture', openPip);
</script>