Sandbox: https://codesandbox.io/s/cranky-kapitsa-op3jh

Repro: type "a" and then after a second "b"

Expected: Eventually you'll see "ab" in all fields. Pending "..." indicator goes away.

Actual: You'll keep seeing "a" in low pri field. Pending "..." indicator is stuck.
counter.current.dispatch(INCREMENT);
      });
      expect(Scheduler).toHaveYielded(['Count: 1']);
      expect(ReactNoop.getChildren()).toEqual([span('Count: 1')]);
      expect(counter.current.count).toBe(1);
      expect(totalRefUpdates).toBe(2);
      
      ReactNoop.render(<Counter ref={counter} />);
      expect(Scheduler).toFlushAndYield(['Count: 1']);
      expect(ReactNoop.getChildren()).toEqual([span('Count: 1')]);
      expect(counter.current.count).toBe(1);
      expect(totalRefUpdates).toBe(2); 
    });
  });
  describe('useTransition', () => {
    it.experimental(
      'delays showing loading state until after timeout',
      async () => {
        let transition;
        function App() {
          const [show, setShow] = useState(false);
          const [startTransition, isPending] = useTransition({
            timeoutMs: 1000,
          });
          transition = () => {
            startTransition(() => {
              setShow(true);
            });
          };
          return (