Summary: This moves the api in line with the java api. hasNewLayout makes for sense than shouldUpdate because the API is not telling css layout to update but is instead just a marker for the user of the API to know if there has been a new layout since last time it checked.
Reviewed By: majak
Differential Revision: D3613695
fbshipit-source-id: 4e16e8d4de90660a09d6e1d3a43c6c5e89349993