Set recents view to be visible from alt+tab

Recents was being initialized but was not
marked as attached to app window. This
was causing it's animator to never make it
View.VISIBLE.

Test: Open any app
On physical keyboard press alt+tab
Observe that overview shows up

fixes: 138396234
Change-Id: I9e6c001242f4552027e79b162fb812f476823a37