Issue 3251 - Simplify messaging from child scripts to parent

lib/child/contentPolicy.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2015 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 52 matching lines @@
  * @return {Boolean} false if the request should be blocked
  */
 function shouldAllow(window, node, contentType, location)
 {
   let response = sendSyncMessage("AdblockPlus:ShouldAllow", {
     contentType: contentType,
     location: location,
     frames: getFrames(window),
     isPrivate: isPrivate(window)
   });
-  if (response.length == 0)
+  if (typeof response == "undefined")
     return true;
 
-  let {allow, collapse, hits} = response[0];
+  let {allow, collapse, hits} = response;
   for (let {frameIndex, contentType, docDomain, thirdParty, location, filter} of hits)
   {
     let context = node;
     if (typeof frameIndex == "number")
     {
       context = window;
       for (let i = 0; i < frameIndex; i++)
         context = context.parent;
       context = context.document;
     }
@@ skipping 262 matching lines @@
         let property = (hasCols ? "cols" : "rows");
         let weights = parentNode[property].split(",");
         weights[index] = "0";
         parentNode[property] = weights.join(",");
       }
     }
     else
       node.classList.add(collapsedClass);
   }
 }