Ref T4222. Earlier, I adjusted the root from webroot/ to webroot/rsrc/. However, this means that all the /rsrc/x/y/z.jpg fragments in CSS are no longer recognized as resource names.
Since we have like 9,000 things in CSS that do url(/rsrc/xyz.jpg) and I don't want to fix/test them all, so just make them work as-is. There's no real reason either setting is better than the other.
(Both URLs also work fine, but the parsed one will be better once we have real CDN support.)