Bug 1383909 - Add observer notification when UserAgentOverrides.jsm finishes initializing. r=mcmanus

MozReview-Commit-ID: BPMzszXmhbC

--HG--
extra : rebase_source : 6bacd03e1a47d0fcd24b561e92a048ed20a75704

netwerk/protocol/http/UserAgentOverrides.jsm

@@ -67,6 +67,7 @@ this.UserAgentOverrides = {
       // UA override might not work correctly.
     }
 
+    Services.obs.notifyObservers(null, "useragentoverrides-initialized");
     gInitialized = true;
   },