Improving accessibility feedback for two state widgets.

1. Added population of sensible text for the state of the
   two state controls such as CheckBox, Switch, etc. This
   is important since if they are in a layout manager which
   fires an accessibility event there should be a description
   of the widget.

bug:5092552

Change-Id: Ie3ca955653563496b84db379ae23a23fe88089a8