Wikia/app — pull request #475 by gabrys (2013-03-04 15:27:14+00:00)
Title: BugId:98734 - Server-side test for adsinhead 

When $wgLoadAdsInHead is set, pageviews get into either adsinhead=1 (50%) or adsinhead=2 (50%) group, which get logged to GA (custom variable 39) and if adsinhead=1 JavaScript ad code is pushed up to HTML

. This allows us to test the performance hit for pushing ad code up in HTML.