Merge "Notify when quickstep gesture starts" into sc-dev am: 1f9fcf87f7 am: be608fe5d7 am: 08a4eb3746

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14630659

Change-Id: Ic5fef9f3da066a1d2cc91e0113aaa1545acc37ae