Summary:
@public
The React Native CLI is not passing the default `maxWorkers` param to Metro, making it run in a single thread and making the development process really slow.
This fixes https://github.com/facebook/metro/issues/253
Reviewed By: mjesun
Differential Revision: D9915500
fbshipit-source-id: d15030af582e99fe20535c07e751cfe12e444f2f