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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

componentDidMount() {
          ReactNoop.yield(`Mount [${this.props.text}]`);
        }
        componentDidUpdate() {
          ReactNoop.yield(`Update [${this.props.text}]`);
        }
        render() {
          return <AsyncText {...this.props} />;
        }
      }
      function App() {
        return (
          <Suspense
            maxDuration={1000}
            fallback={<TextWithLifecycle text="Loading..." />}>
            <TextWithLifecycle text="A" />
            <AsyncTextWithLifecycle ms={100} text="B" />
            <TextWithLifecycle text="C" />
          </Suspense>
        );
      }
      ReactNoop.renderLegacySyncRoot(<App />, () =>
        ReactNoop.yield('Commit root'),
      );
      expect(ReactNoop.clearYields()).toEqual([
        'A',
        'Suspend! [B]',