Add permissions to FeatureFlagService and override api. am: c25fd5aefe

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23715567

Change-Id: I7e773798acfae2e0397af16af658066a3a2a5a76
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>