Merge "Add methods to mark some constraints as optional." into udc-dev am:...

Merge "Add methods to mark some constraints as optional." into udc-dev am: 93d5b793 am: 64ef4481

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/21957228



Change-Id: If5a810bae075f90fb9b6254a5c9ffcd127b96a89
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>