In CL 1140733 (in progress) I added the tethering item to the MultiDevice settings subpage, which involved giving the settings-multidevice-subpage element the CrNetworkListenerBehavior and having it interact with the networkingPrivate API. Ideally, all communication with network infrastructure would occur in the settings-multidevice-tether-item (introduced in CL 1140733), which already has most of it. However, the way the CrNetworkListenerBehavior is implemented, this will require some mild refactoring. We will take care of this once the settings UI is dogfood ready.