Merge "Add ContrastDialog class and tests, activity version" into udc-dev am: 8138fa29 am: 70ca0e7a

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/22411301



Change-Id: I1a985b969c5ad7289879f3b155b5e0e57330f7a8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>