Focus behavior for scroll containers in watch mode

Change default scrolling containers not to request a reveal (parent
scroll) on focus, and to be focusable in touch mode. This helps watch
devices with other input mechanisms that rely on view focus.

Since there's no attribute for the reveal on focus hint, set that in
code. Set focusable in touch mode on the default styles for
ScrollView/HorizontalScrollView. AbsListView already sets this
historically anyway.

Change-Id: I74760f6d523874127da6f6134f0461cc59ce189a