Issue 4129 - Reuse EventEmitter class in messaging module

lib/messaging.js

Index: lib/messaging.js
===================================================================
--- a/lib/messaging.js
+++ b/lib/messaging.js
@@ -12,16 +12,18 @@
  * 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/>.
  */
 
 "use strict";
 
+let {EventEmitter} = require("events");
+
 const MESSAGE_NAME = "AdblockPlus:Message";
 const RESPONSE_NAME = "AdblockPlus:Response";
 
 function isPromise(value)
 {
   // value instanceof Promise won't work - there can be different Promise
   // classes (e.g. in different contexts) and there can also be promise-like
   // classes (e.g. Task).
@@ -116,18 +118,18 @@ LightWeightPort.prototype =
  * Communication port wrapping the message manager API to send and receive
  * messages.
  * @param {nsIMessageManager} messageManager
  * @constructor
  */
 function Port(messageManager)
 {
   this._messageManager = messageManager;
+  this._eventEmitter = new EventEmitter();
 
-  this._callbacks = new Map();
   this._responseCallbacks = new Map();
   this._responseCallbackCounter = 0;
 
   this._handleRequest = this._handleRequest.bind(this);
   this._handleResponse = this._handleResponse.bind(this);
   this._messageManager.addMessageListener(MESSAGE_NAME, this._handleRequest);
   this._messageManager.addMessageListener(RESPONSE_NAME, this._handleResponse);
 }
@@ -203,21 +205,17 @@ Port.prototype = {
     {
       this._responseCallbacks.delete(callbackID);
       callback(processor.value);
     }
   },
 
   _dispatch: function(messageName, payload, sender)
   {
-    let callbacks = this._callbacks.get(messageName);
-    if (!callbacks)
-      return undefined;
-
-    callbacks = callbacks.slice();
+    let callbacks = this._eventEmitter.listeners(messageName);
     let processor = new ResponseProcessor(messageName);
     for (let callback of callbacks)
     {
       try
       {
         processor.add(callback(payload, sender));
       }
       catch (e)
@@ -241,37 +239,27 @@ Port.prototype = {
 
   /**
    * Adds a handler for the specified message.
    * @param {string} messageName message that would trigger the callback
    * @param {Port~messageHandler} callback
    */
   on: function(messageName, callback)
   {
-    let callbacks = this._callbacks.get(messageName);
-    if (callbacks)
-      callbacks.push(callback);
-    else
-      this._callbacks.set(messageName, [callback]);
+    this._eventEmitter.on(messageName, callback);
   },
 
   /**
    * Removes a handler for the specified message.
    * @param {string} messageName message that would trigger the callback
    * @param {Port~messageHandler} callback
    */
   off: function(messageName, callback)
   {
-    let callbacks = this._callbacks.get(messageName);
-    if (!callbacks)
-      return;
-
-    let index = callbacks.indexOf(callback);
-    if (index >= 0)
-      callbacks.splice(index, 1);
+    this._eventEmitter.off(messageName, callback);
   },
 
   /**
    * Sends a message.
    * @param {string} messageName message identifier
    * @param [payload] data to attach to the message
    */
   emit: function(messageName, payload)