Merge "Polish background for controls panel." into tm-qpr-dev am: bb848b65 am: bee18180

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/20668386



Change-Id: I570eb6e7449b30da205d024d1a1c65c511b5476a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>