Last modified: 2012-04-20 12:41:27 UTC
$wgUseSiteJs was added by r6223. The idea was to avoid an extra web server HIT. One usage removed with r107777. There is only one left in OutputPage to add the 'site' resource loader link. I think we could drop that global just like we dropped $wgUseSiteCss.
In the ResourceLoader world I don't think it actually adds a hit either, necessarily...
Indeed. Last I checked ResourceLoader doesn't output links for user/site js/css if the related pages on-wiki are empty or inexistent. They could still serve as a way to prevent wiki-admins from writing JavaScript that is loaded on all pages for all users though, which I think is a valid use case that some mediawiki runners may wish to keep that way.
Marking wontfix per Krinkle comment #2