It's unclear if any HTTP channel clients ever set originalURI != uri (about:credits?); it's also not clear if chrome channel would ever need to know. So we may be able to eliminate the argument.

> It's unclear if any HTTP channel clients ever set originalURI != uri Some extensions sure do. But those would be in the chrome. HTTP redirects do, but those happen in chrome too, right? .url/.desktop files pointing to http:// URIs do, I would think. Where do those happen?

in general, as much should work in the child as possible. if we've got a profile that says this moves the needle, then reassess.