Bug 337168 - Tag leakable object, and also remove the leak.

ChatZilla only.
r=samuel

extensions/irc/js/lib/pref-manager.js

@@ -84,7 +84,7 @@ function PrefManager (branchName, defaultBundle)
     this.prefs = new Object();
     this.prefNames = new Array();
     this.prefRecords = new Object();
-    this.observer = { observe: pm_observe };
+    this.observer = { observe: pm_observe, branch: branchName };
     this.observers = new Array();
 
     this.prefBranchInternal =

extensions/irc/xul/content/commands.js

@@ -2460,6 +2460,7 @@ function cmdLoad(e)
             if ("onPrefChanged" in plugin)
                 prefManager.addObserver(plugin);
             client.prefManager.addObserver(prefManager);
+            client.prefManagers.push(prefManager);
         }
         else
         {