Merge "Invalidate empty pages at the start of wallpaper" into tm-dev am: 16d26136 am: 3322b53e

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/17756831



Change-Id: I51349ef82d5fe3109c3a06486617d949658af9c6
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>