New consent model.

Preserves existing UI buttons and behavior. Replacing with a UI that directly
exposes the relevant fields will come later.
Hm, interesting.
1. I think this code (usually?) doesn't get executed, because the socksToRtc_.onceStopped callback (set up in RemoteInstance.start) sets "this.access.asProxy = false".
2. core.stop sets Core.remoteProxyInstance to null. Is that important? I /believe/ I preserved this behavior, so core.stop already wasn't being called.