Summary:
**Motivation**
The prop validation was run on every render, even in prod which seems odd to me. This adds a dev check to make sure prod build skips the validation.
**Test plan (required)**
There are no changes to the ui.
Closes https://github.com/facebook/react-native/pull/8499
Differential Revision: D3508805
Pulled By: javache
fbshipit-source-id: 68c6a1224e33997f9df93481426daff790ef5bcd
508cc06565