Previously prefs.set broadcast many messages per each changed pref value to all open tabs, background page, popups. This lead to repeated and needless updates of various things like the toolbar icon, reapplying of styles, and whatnot. It could easily take more than 100ms on an average computer with many tabs open.
Now we debounce the broadcast & sync.set and coalesce all values in one object which is then sent just once per destination.
