Merge "Add a flag to show/hide wallpaper dream." into udc-dev am: 2032ce62 am: 0718a68a

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23697465



Change-Id: Ideec58185cbd8d7fa971762b28b58764a99272b7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>