Issue 3251 - Simplify messaging from child scripts to parent

lib/elemHide.js

Index: lib/elemHide.js
===================================================================
--- a/lib/elemHide.js
+++ b/lib/elemHide.js
@@ -75,25 +75,19 @@ let ElemHide = exports.ElemHide =
    */
   applied: false,
 
   /**
    * Called on module startup.
    */
   init: function()
   {
-    let messageManager = Cc["@mozilla.org/parentprocessmessagemanager;1"]
-                           .getService(Ci.nsIMessageListenerManager);
-    let hitHandler = (message => {
-      let result = ElemHide.shouldHide(message.data);
-      let target = message.target.QueryInterface(Ci.nsIMessageSender);
-      target.sendAsyncMessage(message.data.responseMessage, result);
+    Utils.addChildMessageListener("AdblockPlus:ElemHideHit", (data) => {
+      return ElemHide.shouldHide(data);
     });
-    messageManager.addMessageListener("AdblockPlus:ElemHideHit", hitHandler);
-    onShutdown.add(() => messageManager.removeMessageListener("AdblockPlus:ElemHideHit", hitHandler));
 
     Prefs.addListener(function(name)
     {
       if (name == "enabled")
         ElemHide.apply();
     });
     onShutdown.add(() => ElemHide.unapply());