Bug 808215 - Disable social API in private windows for per-window Private Browsing builds.  r=jaws

--HG--
rename : browser/base/content/test/social/browser_social.js => browser/base/content/test/social/browser_social_globalPB.js
extra : rebase_source : 4cd66d38df3af9ba52c224e466ee7268b2cf43de