Merge "Add a flag to show/hide wallpaper dream." into udc-dev am: 2032ce62 am: 2303e22e am: a5ed7bd0 am: 5b873bc4

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



Change-Id: Ie7bb37a261c1309d1687a40b81d26770233f39de
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>