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

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



Change-Id: I8949aee3725454b21846b90313c7b9460bf745e0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>