Summary:
Replace object with cached styles from StyleSheet
Create new style object may cause performance problems
Check that ImageBackground position works the same way.
Closes https://github.com/facebook/react-native/pull/14486
Differential Revision: D5274503
Pulled By: shergin
fbshipit-source-id: 09b81e6f7ae2ada7f68854e409909caafd85e56a