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

lib/elemHide.js

Index: lib/elemHide.js
===================================================================
--- a/lib/elemHide.js
+++ b/lib/elemHide.js
@@ -23,16 +23,17 @@ Cu.import("resource://gre/modules/Servic
 
 let {Utils} = require("utils");
 let {IO} = require("io");
 let {Prefs} = require("prefs");
 let {ElemHideException} = require("filterClasses");
 let {FilterNotifier} = require("filterNotifier");
 let {AboutHandler} = require("elemHideHitRegistration");
 let {TimeLine} = require("timeline");
+let Policy = null;
 
 /**
  * Lookup table, filters by their associated key
  * @type Object
  */
 let filterByKey = Object.create(null);
 
 /**
@@ -55,21 +56,35 @@ let exceptions = Object.create(null);
 
 /**
  * Currently applied stylesheet URL
  * @type nsIURI
  */
 let styleURL = null;
 
 /**
+ * Global stylesheet that should be loaded into content windows.
+ * @type nsIStyleSheet
+ */
+let styleSheet = null;
+
+/**
+ * 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 =
 {
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
+
   /**
    * Indicates whether filters have been added or removed since the last apply() call.
    * @type Boolean
    */
   isDirty: false,
 
   /**
    * Inidicates whether the element hiding stylesheet is currently applied.
@@ -78,36 +93,74 @@ let ElemHide = exports.ElemHide =
   applied: false,
 
   /**
    * Called on module startup.
    */
   init: function()
   {
     TimeLine.enter("Entered ElemHide.init()");
+
+    if (useNew) {
+      // Avoid dependency issue.
+      Policy = require("contentPolicy").Policy;
+    }
+
     Prefs.addListener(function(name)
     {
       if (name == "enabled")
         ElemHide.apply();
     });
-    onShutdown.add(function()
+
+    if (useNew)
+      Services.obs.addObserver(this, "content-document-global-created", true);
+
+    onShutdown.add(() =>
     {
       ElemHide.unapply();
+      if (useNew)
+        Services.obs.removeObserver(this, "content-document-global-created");
     });
 
     TimeLine.log("done adding prefs listener");
 
     let styleFile = IO.resolveFilePath(Prefs.data_directory);
     styleFile.append("elemhide.css");
     styleURL = Services.io.newFileURI(styleFile).QueryInterface(Ci.nsIFileURL);
     TimeLine.log("done determining stylesheet URL");
 
     TimeLine.leave("ElemHide.init() done");
   },
 
+  observe: function (subject, topic, data, additional)
+  {
+    if (topic != "content-document-global-created")
+      return;
+
+    if (!Prefs.enabled)
+      return;
+
+    if (Policy.shouldNeverBlockWindow(subject))
+      return;
+
+    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);
     knownExceptions = Object.create(null);
@@ -224,17 +277,18 @@ let ElemHide = exports.ElemHide =
 
     if (!ElemHide.isDirty || !Prefs.enabled)
     {
       // Nothing changed, looks like we merely got enabled/disabled
       if (Prefs.enabled && !ElemHide.applied)
       {
         try
         {
-          Utils.styleService.loadAndRegisterSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
+          if (!useNew)
+            Utils.styleService.loadAndRegisterSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
           ElemHide.applied = true;
         }
         catch (e)
         {
           Cu.reportError(e);
         }
         TimeLine.log("Applying existing stylesheet finished");
       }
@@ -276,17 +330,20 @@ let ElemHide = exports.ElemHide =
 
         ElemHide.unapply();
         TimeLine.log("ElemHide.unapply() finished");
 
         if (!noFilters)
         {
           try
           {
-            Utils.styleService.loadAndRegisterSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
+            if (!useNew)
+              Utils.styleService.loadAndRegisterSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
+            else
+              styleSheet = Utils.styleService.preloadSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
             ElemHide.applied = true;
           }
           catch (e)
           {
             Cu.reportError(e);
           }
           TimeLine.log("Applying stylesheet finished");
         }
@@ -360,36 +417,28 @@ let ElemHide = exports.ElemHide =
    * Unapplies current stylesheet URL
    */
   unapply: function()
   {
     if (ElemHide.applied)
     {
       try
       {
-        Utils.styleService.unregisterSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
+        if (!useNew)
+          Utils.styleService.unregisterSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
       }
       catch (e)
       {
         Cu.reportError(e);
       }
       ElemHide.applied = false;
     }
   },
 
   /**
-   * Retrieves the currently applied stylesheet URL
-   * @type String
-   */
-  get styleURL()
-  {
-    return ElemHide.applied ? styleURL.spec : null;
-  },
-
-  /**
    * Retrieves an element hiding filter by the corresponding protocol key
    */
   getFilterByKey: function(/**String*/ key) /**Filter*/
   {
     return (key in filterByKey ? filterByKey[key] : null);
   },
 
   /**