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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

<span prop="Loading (1)" />
          <span prop="Loading (2)" />
          <span prop="Loading (3)" />
        </React.Fragment>,
      );
      await advanceTimers(100);
      expect(ReactNoop.flush()).toEqual([
        'Promise resolved [Step: 2]',
        'Step: 2',
      ]);
      expect(ReactNoop.getChildrenAsJSX()).toEqual(
        <React.Fragment>
          <span prop="Step: 2" />
          <span prop="Sibling" />
        </React.Fragment>,
      );
    });
    it(
      'continues rendering asynchronously even if a promise is captured by ' +
        'a sync boundary (default mode)',
      async () => {
        class UpdatingText extends React.Component {
          state = {text: this.props.initialText};
          render() {
            return this.props.children(this.state.text);
          }
        }
        const text1 = React.createRef(null);
        const text2 = React.createRef(null);
        function App() {