Show ASAP for Recents Go and load content after

Recent UX discussion led to decision to show as soon as we have the list
and order and then load the content in after as soon as it comes. This
introduces API in TaskListLoader to facilitate this and default values
for the view when the content is not yet loaded.

Bug: 114136250
Test: Go to recents, see content load in
Change-Id: I6766cf014e3de78894353614157dbc8798031c2f