The back button is really just window.history.back() , but because we need to tell the UI to use the "back-one" animation it's proxied though the FxaModuleUI.

Ideally I'd like the onNext not to have any virtual(ish) methods either, but I didn't want to break too much of the module specific code before getting your feedback. The thought is that there is no predefined "back" and "next" states .. Each module can send the user to "next" or "ToS" or "forgot password" or whatever through setting the correct location.hash. That is my suggestion, I'd very much like feedback on that :)