Merge "Enable blur letterbox wallpaper behind flags" into udc-qpr-dev am: 9c84b517 am: 8e04a4b0

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23874759



Change-Id: I962b757b8ec7b6477145eaa707698ae4b34f89ff
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>