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.
Scheduler.unstable_yieldValue('Foo');
      return (
        <Suspense fallback={<Text text="Initial load..." />}>
          <Suspense
            unstable_avoidThisFallback={true}
            fallback={<Text text="Loading A..." />}>
            <Text text="A" />
            {showB ? (
              <Suspense
                unstable_avoidThisFallback={true}
                fallback={<Text text="Loading B..." />}>
                <AsyncText text="B" ms={5000} />
              </Suspense>
            ) : null}
          </Suspense>
        </Suspense>
      );
    }
    ReactNoop.render(<Foo />);