Summary:
I found that android support library 27.x (https://github.com/facebook/react-native/commit/874cca1ac258ec224bade999722d7a34c307def0) requires compileSdkVersion to be 27. Also found that many FB projects use SDK 27.
Pull Request resolved: https://github.com/facebook/react-native/pull/20777

Differential Revision: D9478431

Pulled By: hramos

fbshipit-source-id: ca100f6b5b39e7d112926124423f9510a0efc291