Merge "Use LayoutManager.onLayoutCompleted as a signal that content has changed" into sc-dev am: d541300f0e am: d8103fc95d

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

Change-Id: I4c769f02711311cb216f4715993437f50ef53bfe