Added backwards compatibility for Chrome's old messaging API

chrome/common.js

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * Copyright (C) 2006-2013 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 38 matching lines @@
         this._target.removeListener(this._wrappedListeners[idx]);
 
         this._listeners.splice(idx, 1);
         this._wrappedListeners.splice(idx, 1);
       }
     }
   };
 
   var MessageEventTarget = function()
   {
-    WrappedEventTarget.call(this, chrome.runtime.onMessage);
+    WrappedEventTarget.call(this, chrome.runtime.onMessage || chrome.extension.onRequest);
   };
   MessageEventTarget.prototype = {
     __proto__: WrappedEventTarget.prototype,
     _wrapListener: function(listener) {
       return function(message, sender, sendResponse)
       {
         listener(message, {tab: sender.tab && new Tab(sender.tab)}, sendResponse);
       };
     }
   };
 
+
   /* API */
 
   ext = {
     backgroundPage: {
-      sendMessage: function(message, responseCallback)
-      {
-        chrome.runtime.sendMessage(message, responseCallback);
-      },
-      getWindow: function()
-      {
-        return chrome.extension.getBackgroundPage();
-      }
+      sendMessage: chrome.runtime.sendMessage || chrome.extension.sendRequest,

[Wladimir Palant, 2013/11/17 06:19:45]

This will error out with "Cannot get property sendMessage of undefined" on
anything older than Chrome 22. You have to check whether chrome.runtime is
actually present.

+      getWindow: chrome.extension.getBackgroundPage
     },
     getURL: chrome.extension.getURL,
     onMessage: new MessageEventTarget(),
     i18n: chrome.i18n
   };
 })();