Fix SysUI crash when launching Chrome from app shelf

* Store entire ActivityManager.RecentTaskInfo for each icon,
  not just the ComponentName.
* Use RecentTaskInfo.persistentId to check if an icon already
  exists.
* Extend RecentTaskInfo to include the actual activity that
  started the task.
* On dragging an icon to the pinned area, use the RecentTaskInfo
  to pin the primary launch intent of the app.

Bug: 22117860
Change-Id: Ia4412ea8e259e53cd7b5babcb79a292b92629db0