Fix torbutton for ESR45
domain-isolator.js has a couple of minor breakages in Firefox 45.
- 
A new ReferenceError is thrown by things like
let mozilla = mozilla || {};. We can change it tolet mozilla = {};. - 
The method
newSOCKSProxyInfowas available in our SOCKS proxy patch. Since we landed that patch with some minor changes, we should now make an equivalent call to built-in Firefox methodnewProxyInfoWithAuth.