Make RotationChangeProvider Threadsafe

Follow up of ag/27767415, lastRotation field is accessed from different thread so should use AtomicInteger

Bug: 344626706
Test: RotationChangeProviderTest
Flag: NONE bugfix
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:7088fab56a7e2ad2d9083a215c4cccbad032c5e0)
Merged-In: Ide5f62028cc29b595cb0266e664d051a27c1263c
Change-Id: Ide5f62028cc29b595cb0266e664d051a27c1263c