Issue 3826 - Filter preference change events

lib/messaging.js

Index: lib/messaging.js
===================================================================
--- a/lib/messaging.js
+++ b/lib/messaging.js
@@ -19,6 +19,8 @@
 
 "use strict";
 
+let {EventEmitter} = require("events");
+
 /**
  * Communication port wrapping ext.onMessage to receive messages.
  *
@@ -26,7 +28,7 @@
  */
 function Port()
 {
-  this._callbacks = Object.create(null);
+  this._eventEmitter = new EventEmitter();
   ext.onMessage.addListener(this._onMessage.bind(this));
 };
 
@@ -34,7 +36,7 @@
   _onMessage: function(message, sender, sendResponse)
   {
     let async = false;
-    let callbacks = this._callbacks[message.type] || [];
+    let callbacks = this._eventEmitter._callbacks[message.type] || [];
 
     for (let callback of callbacks)
     {
@@ -80,10 +82,7 @@
    */
   on: function(name, callback)
   {
-    if (name in this._callbacks)
-      this._callbacks[name].push(callback);
-    else
-      this._callbacks[name] = [callback];
+    this._eventEmitter.on(name, callback);
   },
 
   /**
@@ -94,13 +93,7 @@
    */
   off: function(name, callback)
   {
-    let callbacks = this._callbacks[name];
-    if (callbacks)
-    {
-      let idx = callbacks.indexOf(callback);
-      if (idx != -1)
-        callbacks.splice(idx, 1);
-    }
+    this._eventEmitter.off(name, callback);
   }
 };