Pure stylistic nit: I'm a firm believer in variable name length being a function of the lifetime of the object, i.e. the length in lines of the containing scope. Since responseWriterDelegator is around for only 15 lines, why not simply **d**, or **rwd**?

Similarly, I would propose s/responseWriter/w, and s/request/r (or s/request/req), on the strength of (this sort of prior-art)[http://golang.org/src/pkg/net/http/server.go?s=20466:20526#L740].