Merge "[1/n] Add LetterboxRule to AppCompat Flicker test" into udc-qpr-dev am: 27dd177141

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23917797

Change-Id: I853032298158d3f18bbb1fd07273beeaae53210e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>