Merge "Annotate AttributeSet with @Nullable" into sc-v2-dev am: 6c7c91fe86 am: 820f8b6da4

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/16233502

Change-Id: I28eaea5741bfe0a86ee4e6fb50e775bc7a5937a8