Refactored the abstraction layer to address prerendered pages on Safari caused by leaky abstraction

safari/ext/common.js

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * Copyright (C) 2006-2014 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 145 matching lines @@
           if (!placeholderDetails || !placeholderDetails.content)
             continue;
           if (placeholderDetails.content.indexOf("$") != 0)
             continue;
 
           var placeholderIdx = parseInt(placeholderDetails.content.substr(1));
           if (isNaN(placeholderIdx) || placeholderIdx < 1)
             continue;
 
           var placeholderValue;
-          if (substitutions && substitutions.constructor == Array)
+          if (typeof substitutions != "string")
             placeholderValue = substitutions[placeholderIdx - 1];
           else if (placeholderIdx == 1)
             placeholderValue = substitutions;
 
           msgstr = msgstr.replace("$" + placeholder + "$", placeholderValue || "");
         }
 
         return msgstr;
       }
 
       return "";
     }
   };
 
 
   /* Utils */
 
   ext.getURL = function(path)
   {
     return safari.extension.baseURI + path;
   };
 })();