SystemUI's DreamsDockLauncher now responds to low-level dock
events (Intent.ACTION_DOCK_EVENT) by immediately invoking
the user's selected screen saver.
(The high-level DESK_DOCK behavior is no longer enabled; see
change I7884f65.)
Bug: 5591015
Change-Id: I01a9bc6b181d55493f891ccc220631ddc461808a