Merge "notification stack scroller doesn't need a11y focus" into sc-dev am: 49c7bc6618 am: 1ab91ceac2 am: cde9fef4c3

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

Change-Id: Ic1b1a68ceb7a55375d47a5930016546c8be94d95