Merge "notification stack scroller doesn't need a11y focus" into sc-dev am: 49c7bc66 am: 1ab91cea am: cde9fef4 am: 307807bc

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

Change-Id: I0e48243f283416caccbea580949008857453d96c