Define FeatureFlagsService. am: 4f7ccd42f1

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23715565

Change-Id: I9b661eddeb44fba3e2179e6a52f412f6d46e3269
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>