Merge "[flexiglass] Enable toggling legacy SysUI on/off." into udc-qpr-dev am: 3c61576c

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/24058407



Change-Id: Ib2148900620fd30414743b59db5547ecdc18e192
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>