rewrite_host_and_protocol

# File actionpack/lib/action_view/asset_paths.rb, line 67
    def rewrite_host_and_protocol(source, protocol = nil)
      host = compute_asset_host(source)
      if host && !is_uri?(host)
        if (protocol || default_protocol) == :request && !has_request?
          host = nil
        else
          host = "#{compute_protocol(protocol)}#{host}"
        end
      end
      host ? "#{host}#{source}" : source
    end