base

Animate public/private notification layouts

This change move the boolean whether we hide sensitive contents into
AmbientState, which makes it consistent with the other stack states
and allows for a orchestrated transition between public/private
layouts. We need this transition when going into the full shade.

Bug: 16291973
Change-Id: I379a6119b5b73eca900a4a2ba9d5ec95b293e487