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

<!DOCTYPE html>
<head>
<meta charset="utf-8">
<title>Autopip On a Delay</title>
<script src="../../webrtc/test_functions.js"></script>
<script src="../../webrtc/getusermedia.js"></script>
</head>
<body>
</body>
<script>
function openPip() {
  // Delay opening PiP, but still within the user gesture window.
  setTimeout(() => {
    documentPictureInPicture.requestWindow();
  }, 100);
}

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