ActionProvider API update

* Add ActionProvider#overridesItemVisibility and isVisible.
  These methods allow an ActionProvider to override the
  visibility of a MenuItem that it is bound to. If a MenuItem
  has been explicitly hidden by the application, it will not
  be visible.

* Change MediaRouteActionProvider to not require a MediaRouter
  callback, to avoid extra lifecycle management headaches.

Change-Id: I606fa98b3a6a3e60a953dd024274f9bf9c67acdd