Some apps have no printing option with lprng

We are testing Ubuntu Precise, and one of the problems we encounter is that some X applications don't have an option to print using the generic lpr command. For example, Ubuntu packaged Firefox and also Google chrome (neither from the native print dialogue, nor when I click "Print using system dialog". The only option we get from the print dialog is to print to file.

In contrast, some other applications like the Libre Office or Acrobat do provide a means to print using the lpr or lp command.

We are using lprng as our printing system, and it's working fine otherwise, in as printing from the command line or from the applications that use the command line printing interface.

Any ideas how to talk Firefox and friends into offer printing using lpr?