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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

// one performs Sync work, rerendering the Suspense.
  if ((boundaryFiber.mode & ConcurrentMode) !== NoContext) {
    if (root === nextRoot && nextRenderExpirationTime === suspendedTime) {
      // 
      // 
      nextRoot = null;
    }
  }
  scheduleWorkToRoot(boundaryFiber, retryTime);
  if ((boundaryFiber.mode & ConcurrentMode) === NoContext) {
    // 
    // 
    // 
    scheduleWorkToRoot(sourceFiber, retryTime);
    const sourceTag = sourceFiber.tag;
    if (sourceTag === ClassComponent && sourceFiber.stateNode !== null) {
      // 
      // 
      // 
      const update = createUpdate(retryTime);
      update.tag = ForceUpdate;
      enqueueUpdate(sourceFiber, update);
    }
  }
  const rootExpirationTime = root.expirationTime;
  if (rootExpirationTime !== NoWork) {
    requestWork(root, rootExpirationTime);
  }
}
function scheduleWorkToRoot(fiber: Fiber, expirationTime): FiberRoot | null {