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**Do you want to request a *feature* or report a *bug*?**
Not sure if its a bug or a feature request.

**What is the current behavior?**
The component given as a fallback to Suspense is remounted each time a lazy child resolves.

https://codesandbox.io/s/z6v6x3n1np
This example shows how a fallback component, which counts up, is mounted more than once.

**What is the expected behavior?**
The fallback is mounted once and is only unmounted when all lazy children are resolved.
In the example the counter would run up to 9.

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

const root = (workInProgress.stateNode: FiberRoot);
  if (root.pendingContext) {
    pushTopLevelContextObject(
      workInProgress,
      root.pendingContext,
      root.pendingContext !== root.context,
    );
  } else if (root.context) {
    
    pushTopLevelContextObject(workInProgress, root.context, false);
  }
  pushHostContainer(workInProgress, root.containerInfo);
}
function updateHostRoot(current, workInProgress, renderExpirationTime) {