# File lib/webrick/httpproxy.rb, line 56
    def choose_header(src, dst)
      connections = split_field(src['connection'])
      src.each{|key, value|
        key = key.downcase
        if HopByHop.member?(key)          || # RFC2616: 13.5.1
           connections.member?(key)       || # RFC2616: 14.10
           ShouldNotTransfer.member?(key)    # pragmatics
          @logger.debug("choose_header: `#{key}: #{value}'")
          next
        end
        dst[key] = value
      }
    end