Merge "Use LayoutManager.onLayoutCompleted as a signal that content has changed" into sc-dev am: d541300f0e am: f231c45c27

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

Change-Id: Ib4fbae930f38a0f210be452fd311e0e46fd10a9e