Merge "Promote FeatureFlag best practices in notifications code & tests" into udc-qpr-dev am: febba3b65f am: ebee1d214a

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23984923

Change-Id: I88980b1b7fc1d21289c176f9ba2c666a50b1c110
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>