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**Do you want to request a *feature* or report a *bug*?**
bug, I believe, unless I misunderstand how it works
**What is the current behavior?**
Given a `Suspense` inside `Suspense` case like
```
<Suspense fallback="Fallback 1">
  <LazyText1 text="First text" />
  <Suspense fallback="Fallback 2">
    <LazyText2 text="Second text!" />
  </Suspense>
</Suspense>
```

Promises in `LazyTexts` start resolving at the same time, but if `LazyText2` is resolved first it never renders, `Fallback 2` stays.

Result:
```
First text

Fallback 2
```

Please see https://codesandbox.io/s/234o4zry7n

**What is the expected behavior?**

Every `LazyText` displayed in the end
```
First text

Second text!
```

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
react, react-dom 16.6.0

ReactTestRenderer.unstable_yield('Component:' + children);
          return children;
        }
        let renderer;
        
        throwInOnWorkScheduled = true;
        expect(() => {
          SchedulerTracing.unstable_trace('event', mockNow(), () => {
            renderer = ReactTestRenderer.create(<Component>fail</Component>, {
              unstable_isConcurrent: true,
            });
          });
        }).toThrow('Expected error onWorkScheduled');
        throwInOnWorkScheduled = false;
        expect(onWorkScheduled).toHaveBeenCalled();
        
        renderer = ReactTestRenderer.create(<Component>succeed</Component>, {
          unstable_isConcurrent: true,
        });
        expect(renderer).toFlushAndYield(['Component:succeed']);
        const tree = renderer.toTree();
        expect(tree.type).toBe(Component);
        expect(tree.props.children).toBe('succeed');
      });
      it('should cover errors thrown in onWorkStarted', () => {
        function Component({children}) {