Console error: "window.controllers is deprecated"

[diracdeltas]

To repro, visit a page like https://developer.mozilla.org/en-US/docs/Glossary/Expando in Firefox and watch the javascript console.

HTTPS Everywhere uses custom window controllers in the getExpando and setExpando methods, where the expando is essentially the list of applicable rules for a given DOM window. Mozilla folks tell me that we should be using WeakMaps keyed by the window instead of StorageControllers (which is what Privacy Badger Firefox does). IIRC, our expando implementation isn't e10s compatible anyway.