Merge "Use LayoutManager.onLayoutCompleted as a signal that content has changed" into sc-dev am: d541300f0e am: d8103fc95d am: 0e7a729f37

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

Change-Id: I44078a1c9531c0eb33374dfe7fc009d28334dabe