Does Google Analytics need cross domain tracking in Facebook Instant Articles? - facebook

Question

Our site publishes articles on WordPress and also provides some of these posts to Facebook Instant Articles in a feed.
I'm in the process of upgrading our site's Google Analytics code to Universal Analytics. We're using the dc.js version with display features.
On our current Facebook Instant Article template the GA code is like
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'XXXXXXXXXXXXX']);
_gaq.push(['_setDomainName', 'none']);
_gaq.push(['_setAllowLinker', true]);
_gaq.push(['_setCampSourceKey', 'itx']);
_gaq.push(['_setReferrerOverride', 'http://fbia.facebook.com']);
_gaq.push(['_trackPageview']);
I don't understand all of these settings myself. From what I read the _setDomainName value sets cookie access to the current domain only, whereas _setAllowLinker allows GA to link activity tracked on different domains.
I do know that itx is an argument we commonly append to URLs to indicate the source of clicks. And with _setReferrerOverride we set an arbitrary referrer value that allows us to separate out FBIA activity in the GA reports.
My question is, do I need to do cross-domain tracking with FBIA articles? And if so, how would I do it?
It seems that the Universal Analytics way of doing cross-domain is to specify the "other" domains you want to link to in a linker:autolink statement. But what domain would I specify for an FBIA article?
In case useful to anybody else, this is how I think the legacy GA code could be translated to Universal on FBIA tracking.
ga('create', 'XXXXXXXXXXXXX', 'auto', {'allowLinker': true});
ga('require', 'linker');
ga('linker:autoLink', ['xxxxx.com']);
ga('require', 'displayfeatures');
ga('set', 'campaignSource', 'Facebook');
ga('set', 'campaignMedium', 'Social Instant Article');
ga('set', 'title', ia_document.title);
ga('set', 'referrer', 'http://fbia.facebook.com');
ga('send', 'pageview');