Merge "notification stack scroller doesn't need a11y focus" into sc-dev am: 49c7bc66 am: 0e3a87bc am: 3f671a36 am: a090a051

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15692791

Change-Id: I908172edaf34811a46604b920706f0048b4ae348