Issue 1663 - Emulate background page and implement proper message responder

ext/background.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
  * 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/>.
  */
 
 (function(global)
 {
   if (!global.ext)
     global.ext = {};
 
   window.addEventListener("load", function()
   {
     parent.postMessage({
       type: "backgroundPageLoaded"
     }, "*");
   }, false)
 
-  var removalListeners = [];
-  ext.onPageRemoved = {
-    addListener: function(listener)
+  function PageMap()
+  {
+    this._keys = [];
+    this._values = [];
+  }
+  PageMap.prototype = {
+    keys: function()
     {
-      if (removalListeners.indexOf(listener) < 0)
-        removalListeners.push(listener)
+      return this._keys.map(function(source)
+      {
+        return new global.ext.Page(source);
+      });
+    },
+
+    get: function(page)
+    {
+      return this._values[this._keys.indexOf(page._source)];
+    },
+
+    set: function(page, value)
+    {
+      var index = this._keys.indexOf(page._source);
+      if (index < 0)
+      {
+        index = this._keys.push(page._source) - 1;
+
+        var callback = function()
+        {
+          page._source.removeEventListener("unload", callback, false);
+          this.delete(page);
+        }.bind(this);
+        page._source.addEventListener("unload", callback, false);
+      }
+      this._values[index] = value;
+    },
+
+    delete: function(page)
+    {
+      var index = this._keys.indexOf(page._source);
+      if (index >= 0)
+      {
+        this._keys.splice(index, 1);
+        this._values.splice(index, 1);
+      }
     }
   };
 
-  parent.addEventListener("unload", function()
-  {
-    var comparator = function(page)
-    {
-      return page._source == parent;
-    };
-
-    for (var i = 0; i < removalListeners.length; i++)
-      removalListeners[i](comparator);
-  }, false);
+  global.ext.PageMap = PageMap;
 })(this);