Controls UI - Lock screen support

Show controls on the lock screen if the user has chosen to show
sensitive controls. All touches when locked should go through bouncer,
which will force a global dialog dismiss before proceeding.

Bug: 152531337
Fixes: 155402810
Fixes: 154669090
Test: manual

Change-Id: Ib5a305e58a40dd9df5ae2e0f74c5c9bad2edc976