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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

} from './ReactFiberScheduler';
import invariant from 'shared/invariant';
import maxSigned31BitInt from './maxSigned31BitInt';
import {
  NoWork,
  Sync,
  expirationTimeToMs,
  LOW_PRIORITY_EXPIRATION,
} from './ReactFiberExpirationTime';
import {findEarliestOutstandingPriorityLevel} from './ReactFiberPendingPriority';
import {reconcileChildren} from './ReactFiberBeginWork';
function createRootErrorUpdate(
  fiber: Fiber,
  errorInfo: CapturedValue<mixed>,
  expirationTime: ExpirationTime,
): Update<mixed> {
  const update = createUpdate(expirationTime);
  
  update.tag = CaptureUpdate;
  
  
  update.payload = {element: null};
  const error = errorInfo.value;
  update.callback = () => {
    onUncaughtError(error);
    logError(fiber, errorInfo);
  };
  return update;
}
function createClassErrorUpdate(