unlocking during event dispatching is undefined

[marcoscaceres]

Consider:

  promise_test(async t => {
    await test_driver.bless("request full screen", () => {
      return document.documentElement.requestFullscreen();
    });
    const newOrientation = getOppositeOrientation();
    const pMustReject = screen.orientation.lock(newOrientation);
    const pMustResolve = new Promise(r => {
      screen.orientation.onchange = () => {
        r(screen.orientation.unlock());
      };
    });
    await promise_rejects(t, new TypeError(), pMustReject);
    await pMustResolve;
    return document.exitFullscreen();
  }, "Unlocking screen orientation during change event causes orientationPendingPromise to reject");

Presumedly, calling unlock() during onchange would cause the [[orientationPendingPromise]] to reject.

[Johanna-hub]

The test is here web-platform-tests/wpt#15834

[marcoscaceres]

This is now specified: Event fires, promise resolves.