Summary:
== API Breaking Change ==
- Add unit tests to ensure that NavigationStateUtils does the right thing.
- Remove the logics that lets NavigationStateUtils accept empty value as input
and return a new state.
- Remove the method `NavigationStateUtils.getParent`, `NavigationStateUtils.set`. These methods are rarely used and they can be replaced by other methods.
Reviewed By: ericvicenti
Differential Revision: D3374934
fbshipit-source-id: 0fdf538d014d7c5b4aa1f15a0ee8db9dc91e33cd
67002e8ae3