Comment 151 for bug 25830

> (do we expect embeddors to implement nsIExternalHelperAppService?)

I'm tempted to say "no". We have hooks already to modify behavior; changing it
altogether would have too many security implications to be worth supporting, I think. We
should just clearly document that this is an interface exposed by gecko and move
towards freezing it, I think.... (not in the current state, though).

> If we want to ever replace nsIExternalHelperAppService::doContent with
> nsIURIContentListener2::doContent

I think this is a good goal, and when we do this we should revisit nsIDispatchable and its
implementation with that expanded role in mind...