[Plugin: W3 Total Cache] putting js and css files from wp-content/plugins on cdn

I am trying to use W3TC for its CDN support, but looking at my page, it looks like it’s not using the CDN for any of the js or css files in the wp-content/plugins directory. Short of listing them all in the custom files section, how can I get W3TC to use the CDN for these files? I’m not using any of the other W3TC features (I use varnish on this site).

Thanks,
Chris