Summary:
Closes#4290
`mostRecentEventCount` was always being set after `text` on iOS, so let's be really explicit about the order here as we were doing on Android: always call `setNativeProps` providing the `mostRecentEventCount` before we call `onChange` or `onChangeText`.
I also ripped out storing `mostRecentEventCount` in the state, which isn't necessary since we're always doing it through `setNativeProps`.
Closes https://github.com/facebook/react-native/pull/4588
Reviewed By: svcscm
Differential Revision: D2754565
Pulled By: nicklockwood
fb-gh-sync-id: a1401f39b4e19248095517c2a3503cd2af59fa47
c8108bdbe1