Merge "ScreenDecorHwcLayer: better debugging for the transparent region" into tm-dev am: bdf11a99 am: 997109d1

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/17261807

Change-Id: I6fa09361823cc2b95b7bbe8bd26f21300e14b619