network.proxy.socks_remote_dns allows for the ability toresolve DNS names through a SOCKS server. Rather than always resolving through the SOCKS server, please consider adding an interface, similar to nsIProtocolProxyFilter, that would enable extensions and other clients to dynamically determine whether to resolve a given domain through a proxy or not, and through which proxy. The interface's signature could be, for example: nsIProxyInfo applyFilter(in nsIURI aURI, in nsIProxyInfo aProxy) with a corresponding interface for registering/unregistering filters (like nsIProtocolProxyService.registerFilter() and nsIProtocolProxyService.unregisterFilter()).
This is already handled by nsIProtocolProxyFilter.applyFilter. Just conditionally return a nsIProxyInfo instance with the 4th argument true/false. Closing as RESOLVED - WONTFIX.