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: I3274cb7f03f63e1fa99a9ca06759972ce2a51309
(cherry picked from commit 30e9d28c)