Merge "Use LayoutManager.onLayoutCompleted as a signal that content has changed" into sc-dev am: d541300f0e am: 96592dedc2

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14939014

Change-Id: I10a0dc22ce290f1c86cf65f21210ecaceea14f89