Issue 521- Inject our stylesheet on per-site basis rather than globally

lib/elemHide.js

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * Copyright (C) 2006-2014 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
@@ skipping 49 matching lines @@
  */
 let styleURL = null;
 
 /**
  * Global stylesheet that should be loaded into content windows.
  * @type nsIStyleSheet
  */
 let styleSheet = null;
 
 /**
- * Use new way of injecting styles per Window that exists since Firefox 33.
+ * Use the new way of injecting styles per window that exists since Firefox 33.
  * @type boolean
  */
 let useNew = ('preloadSheet' in Utils.styleService);
 
 /**
  * Element hiding component
  * @class
  */
 let ElemHide = exports.ElemHide =
 {
@@ skipping 53 matching lines @@
   {
     if (topic != "content-document-global-created")
       return;
 
     if (!Prefs.enabled)
       return;
 
     if (Policy.shouldNeverBlockWindow(subject))
       return;
 
-    try
-    {
-      let utils = subject.QueryInterface(Ci.nsIInterfaceRequestor)
-                         .getInterface(Ci.nsIDOMWindowUtils);
-      utils.addSheet(styleSheet, Ci.nsIStyleSheetService.USER_SHEET);
-    }
-    catch (e)
-    {
-      Cu.reportError(e);
+    if (styleSheet)
+    {
+      try
+      {
+        let utils = subject.QueryInterface(Ci.nsIInterfaceRequestor)
+                           .getInterface(Ci.nsIDOMWindowUtils);
+        utils.addSheet(styleSheet, Ci.nsIStyleSheetService.USER_SHEET);
+      }
+      catch (e)
+      {
+        Cu.reportError(e);
+      }
     }
    },
 
   /**
    * Removes all known filters
    */
   clear: function()
   {
     filterByKey = Object.create(null);
     keyByFilter = Object.create(null);
@@ skipping 162 matching lines @@
       {
         ElemHide.isDirty = false;
 
         ElemHide.unapply();
         TimeLine.log("ElemHide.unapply() finished");
 
         if (!noFilters)
         {
           try
           {
-            if (!useNew) {
+            if (!useNew)
               Utils.styleService.loadAndRegisterSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
-            } else {
+            else
               styleSheet = Utils.styleService.preloadSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
-            }
             ElemHide.applied = true;
           }
           catch (e)
           {
             Cu.reportError(e);
           }
           TimeLine.log("Applying stylesheet finished");
         }
 
         FilterNotifier.triggerListeners("elemhideupdate");
@@ skipping 107 matching lines @@
 
       if (specificOnly && (!domains || domains[""]))
         continue;
 
       if (filter.isActiveOnDomain(domain) && !this.getException(filter, domain))
         result.push(filter.selector);
     }
     return result;
   }
 };