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

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



Change-Id: Idc6cd48ebaeae2aa0cb318cf27ff2eb680078992
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>