Summary:
Motivation: when you receive error like `scrollToIndex out of range: 5 vs -1` it's not immediately clear if I requested 5 or -1. This will make the error a little easier to understand.
## Changelog
not needed
Pull Request resolved: https://github.com/facebook/react-native/pull/25973
Test Plan: not needed, tests must pass
Differential Revision: D16708522
Pulled By: osdnk
fbshipit-source-id: 8dfcbd95ff0f42805dbe32cd57969a93aea55add
Vojtech NovakandFacebook Github Bot
bef87b648c