Issue 3705 - Don't rely on info.platform when checking for availability of the chrome.* API

webrequest.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 73 matching lines @@
   setTimeout(onBeforeRequestAsync, 0, page, urlString,
                                       type, docDomain,
                                       thirdParty, key,
                                       specificOnly, filter);
 
   return !(filter instanceof BlockingFilter);
 }
 
 ext.webRequest.onBeforeRequest.addListener(onBeforeRequest);
 
-if (platform == "chromium")
+if (typeof chrome == "object")
 {
   function onHeadersReceived(details)
   {
     var page = new ext.Page({id: details.tabId});
     var frame = ext.getFrame(details.tabId, details.frameId);
 
     if (!frame || frame.url.href != details.url)
       return;
 
     for (var i = 0; i < details.responseHeaders.length; i++)
     {
       var header = details.responseHeaders[i];
       if (header.name.toLowerCase() == "x-adblock-key" && header.value)
         processKey(header.value, page, frame);
     }
   }
 
   chrome.webRequest.onHeadersReceived.addListener(
     onHeadersReceived,
     {
       urls: ["http://*/*", "https://*/*"],
       types: ["main_frame", "sub_frame"]
     },
     ["responseHeaders"]
   );
 }