before_sending

# File actionpack/lib/action_dispatch/http/response.rb, line 521
    def before_sending
      # Normally we've already committed by now, but it's possible (e.g., if the
      # controller action tries to read back its own response) to get here before
      # that. In that case, we must force an "early" commit: we're about to freeze the
      # headers, so this is our last chance.
      commit! unless committed?

      @request.commit_cookie_jar! unless committed?
    end