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: 2cb07df6

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



Change-Id: I4f2d3d2d2c17d197ffac5099dae1c00b6c8a3e8e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>