Adding a callback to ShareActionProvider + make ActivityChooserView popup hide on action bar hide.

1. Added a callback to ShareActionProvider allowing clients to be notified
   when an activity is chosed given them a change to say update their UI and
   also decide whether to handle the activity launch themselves.

2. The popup of the ActivityChooserView was not hiding on hiding the action bar.

bug:5094963
bug:5095004

Change-Id: I6c8e8cc1f22d07e707e2218eb108f9101417b23b