Rework action bar menus.

Fix bug 3328810 - remove icons from action bar overflow menu.  Popup
menus now will not show icons. Give popup menu items a minimum width.
Alter the sizing of popup menus.

Fix bug 3192635 - revise rules for action menu dividers. Dividers now
appear between the overflow button and any other items next to it, and
anywhere they disambiguate touch targets between text and other
content. Action views are on their own and should include their own
dividers if needed.

Remove dividers from around action bar spinners and tabs.

Change-Id: I935b48b473606ac2adde5e2b251bf30ebe2a3da9