This CL before, onChanged(null) will cause PreferenceGroup
didn't update UI in ConnectedDeviceDashboardFragment.
This CL remove onChanged(null) and set unvisible of SliceView
in the constructor.
Bug: 142220754
Test: make -j42 RunSettingsRoboTests
Change-Id: Ib20db373430589c5c5efbe8a4c866b7fae4f3399