Issue 3138 - Improve how context menu "block element" handles iframes

lib/filterComposer.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 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 138 matching lines @@
         filters.push(docDomain.replace(/^www\./, "") + "##" + selector);
     }
   }
 
   return {filters: filters, selectors: selectors};
 }
 
 let contextMenuItem = {
   title: ext.i18n.getMessage("block_element"),
   contexts: ["image", "video", "audio"],
-  onclick: page =>
+  onclick: (page, info) =>
   {
-    page.sendMessage({type: "composer.content.contextMenuClicked"});
+    page.sendMessage(
+      {type: "composer.content.contextMenuClicked"}, undefined, info.frameId
+    );
   }
 };
 
 function updateContextMenu(page, filter)
 {
   page.contextMenus.remove(contextMenuItem);
 
   if (typeof filter == "undefined")
     filter = checkWhitelisted(page);
   if (!filter && Prefs.shouldShowBlockElementMenu && readyPages.has(page))
@@ skipping 62 matching lines @@
     baseURL: message.baseURL,
     page:    sender.page,
     frame:   sender.frame
   });
 });
 
 ext.pages.onLoading.addListener(page =>
 {
   page.sendMessage({type: "composer.content.finished"});
 });