1. Adding a widget for sharing contenet with other applications.
The widget orders the share targets based on previous shares.
It displays the share target list as either a popup anchored to
itslef or as a dialog.
2. Added a ShareDataModel that will back widgets or other classes
that are interested in share targets for a given intent ordered
according to share history. This class is backing the ShareView
3. Added ActionProvider mechanism for the MenuItems. The action
provider of a menu creates the action view as well as performs
a default action if the menu item is on the overflow menu and
is triggered but none of the menu callback has handled that.
bug:4590827
Change-Id: Iaa4add2df2538b8c6c7edbeaf2880486d4fd75c5
51ac0e94a8