Content-Length on all responses, this requests and stores both gzip and non gzip responses natively

content-length.vcl

sub vcl_hash
{
  if (req.url ~ "xxx") {
    set req.http.X-Accept-Encoding = req.http.Accept-Encoding;
    hash_data(req.http.Accept-Encoding);
  }
}

sub vcl_backend_fetch
{
  if (req.url ~ "xxx") {
    set bereq.http.Accept-Encoding = bereq.http.X-Accept-Encoding;
  }
}

sub vcl_backend_deliver
{
  if (req.url ~ "xxx") {
    set beresp.do_stream = false;
  }
}