Summary:
When throttling scroll events with `scrollEventThrottle`, `onScroll`
is not guaranteed to be fired for the final scroll position
of the `ScrollView`. This can cause a component to render UI that
is consistent with the resting scroll position of the `ScrollView`.
This commit guarantees that an `onScroll` event will be fired for
the resting scroll position of the `ScrollView`.
**Test plan (required)**
Verified commit fixes a reduced repro. Also tested fix in a larger app.
Adam Comella
Microsoft Corp.
Closes https://github.com/facebook/react-native/pull/7366
Differential Revision: D3269303
Pulled By: javache
fb-gh-sync-id: f68ecb7e9c18d1ac255c6f872fb7eb4aadd07799
fbshipit-source-id: f68ecb7e9c18d1ac255c6f872fb7eb4aadd07799
deef8aade2