chromium/src/third_party/blink/web_tests/external/wpt/feature-policy/resources/feature-policy-battery.html

<script>
'use strict';

Promise.resolve().then(() => navigator.getBattery()).then(battery => {
  window.parent.postMessage({ enabled: true }, '*');
}, error => {
  window.parent.postMessage({ enabled: false }, '*');
});
</script>