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/>.
  */
 
-window.addEventListener("load", function()
+(function(global)
 {
-  parent.postMessage({
-    type: "backgroundPageLoaded"
-  }, "*");
-}, false)
+  if (!global.ext)
+    global.ext = {};
+
+  window.addEventListener("load", function()
+  {
+    parent.postMessage({
+      type: "backgroundPageLoaded"
+    }, "*");
+  }, false)
+
+  function PageMap()
+  {
+    this._keys = [];
+    this._values = [];
+  }
+  PageMap.prototype = {
+    keys: function()
+    {
+      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);
+      }
+    }
+  };
+
+  global.ext.PageMap = PageMap;
+})(this);