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.
const [reducer, setReducer] = useState(() => reducerA);
        const [count, dispatch] = useReducer(reducer, 0);
        useImperativeHandle(ref, () => ({dispatch}));
        if (count < 20) {
          dispatch('increment');
          
          if (reducer === reducerA) {
            setReducer(() => reducerB);
          } else {
            setReducer(() => reducerA);
          }
        }
        Scheduler.unstable_yieldValue('Render: ' + count);
        return <Text text={count} />;
      }
      Counter = forwardRef(Counter);
      const counter = React.createRef(null);
      ReactNoop.render(<Counter ref={counter} />);
      expect(Scheduler).toFlushAndYield([
        
        
        'Render: 0',
        'Render: 10',
        'Render: 11',