Navigation bar size scaling (2 of 2)

Summary:
Feature is disabled when device is in a state where a
Navigation bar is not present. Summary updates feature status
accordingly.

Depends on D437

Change-Id: I73ac0f339cd42561a423ba967120f9c186e43917

Test Plan: the win keeps rolling ;D

Reviewers: synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D439