Merge "Keep track of two top wallpapers to improve the control over each."...

Merge "Keep track of two top wallpapers to improve the control over each." into udc-dev am: a54b7778 am: cfb05591 am: bf3d21fb am: 36b7b37b

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/22336602



Change-Id: I3db8c9c40d0a0ae5e15ce002802e299635ea2af0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>