Detect and handle the case of our own typo correction extension being installed in parallel

lib/typoBootstrap.js

 /*
- * This Source Code is subject to the terms of the Mozilla Public License
- * version 2.0 (the "License"). You can obtain a copy of the License at
- * http://mozilla.org/MPL/2.0/.
+ * This file is part of the Adblock Plus,
+ * Copyright (C) 2006-2012 Eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 /**
  * @fileOverview Adds typo correction feature
  */
 
 Cu.import("resource://gre/modules/AddonManager.jsm");
 
-let {TimeLine} = require("timeline");
 let {Prefs} = require("prefs");
-TimeLine.log("Done loading preferences");
-
 let urlfixerID = "{0fa2149e-bb2c-4ac2-a8d3-479599819475}";
 let addonListener = null;
 
 function init()
 {
   if (!Prefs.correctTyposAsked || (Prefs.correctTyposAsked && Prefs.correctTypos))
   {
     AddonManager.getAddonByID(urlfixerID, function(addon)
     {
       startTypoCorrection(addon && addon.isActive);
     });
   }
   else
   {
-    function onPrefChange(name)
+    let onPrefChange = function(name)
     {
       if (name == "correctTypos" && Prefs[name])
       {
         init();
         Prefs.removeListener(onPrefChange);
       }
     }
     
     Prefs.addListener(onPrefChange);
   }
@@ skipping 23 matching lines @@
       {
         if (addon.id == urlfixerID)
           startTypoCorrection(true);
       },
       onUninstalled: function(addon)
       {
         if (addon.id == urlfixerID)
           startTypoCorrection(false);
       }
     }
+    
     AddonManager.addAddonListener(addonListener);
+    onShutdown.add(function() AddonManager.removeAddonListener(addonListener));
   }
 }
 
 init();