chromium/third_party/blink/manual_tests/scheduling-isInputPending-pointer-lock.html

<!DOCTYPE html>
<html>
<head>
  <meta charset=utf-8 />
  <title>IsInputPending: pointer locked elements may detect pending input</title>
  </title>
  <p>
    This test should be run under <code>--enable-blink-features=ExperimentalIsInputPending</code>.
  </p>
  <p>
    Verify that input is detected with and without pointer locking for each frame, and that sibling and child frames cannot observe pending input.
  </p>
</head>
<p id="text-detected" style="color: green; display: none">Input detected</p>
<p id="text-not-detected" style="color: red">Input not detected</p>
<p><button id="pointer-locker">Lock pointer</button></p>
<script>

const NUM_CHILD_FRAMES = 2;
const PERIOD_MS = 20;

const iipOptions = {includeContinuous: true};

const detectedText = document.querySelector('#text-detected');
const notDetectedText = document.querySelector('#text-not-detected');

setInterval(() => {
  for (const end = performance.now() + PERIOD_MS; performance.now() < end;) {}
  const detected = navigator.scheduling.isInputPending(iipOptions);

  detectedText.style.display = detected ? '' : 'none';
  notDetectedText.style.display = detected ? 'none' : '';
}, PERIOD_MS);

document.querySelector('#pointer-locker').addEventListener('click', e => {
  e.target.requestPointerLock();
});

if (window.top === window.self) {
  for (let i = 0; i < NUM_CHILD_FRAMES; i++) {
    // Add child frames if we're not already one.
    const subframe = document.createElement('iframe');
    subframe.width = 640;
    subframe.height = 240;
    subframe.src = location.href;
    document.body.appendChild(subframe);
  }
}

</script>
</html>