square/okhttp — pull request #380 by swankjesse (2013-12-30 01:54:20+00:00)
Title: Make RawHeaders, RequestHeaders and ResponseHeaders immutable.

This introduces a new, poorly-named class ResponseStrategy
that pulls some code out of ResponseHeaders. That was necessary
because the old method mutated itself and its parameters in
place.

Obvious follow-up for this is to combine ResponseHeaders with
Response, and RequestHeaders with Response.