Result handlers may not return results if the screen is rotated

This issue came to mind while reviewing !354 (merged) - SetupActivity#onClick() uses the onResultUi() method of a UiResultHandler to start the next activity. If the screen's rotated before the handler returns, the original activity will be destroyed, so the handler will never call onResultUi(). The outcome, as far as I can see, will be a progress wheel that spins forever.

Similar problems may exist elsewhere. Most of the time we use ResultHandlers to update the state of the current activity or fragment, and we reload everything if the activity or fragment's recreated, so it doesn't matter if results are lost during rotation. But there may be some places like this one where we depend on the result being returned.