RESTRICT AUTOMERGE

Allow CDM to hide overlays

Since CDM has sensitive user consent UIs, it should be able to hide
non-system overlays

Test: use a 3p overlay app with a visible overlay to ensure overlay disappears when CDM is shown
Bug: 171221090
Change-Id: I78673b7b95f4c3cb31fab180201eb17c9123bddf
Merged-In: I78673b7b95f4c3cb31fab180201eb17c9123bddf