Merge "Add a flag to show/hide wallpaper dream." into udc-dev am: 2032ce62 am: 2303e22e am: a5ed7bd0

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



Change-Id: I427b122a4b5afbbd73216c5fc328dd3703bfd278
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>