Issue 2658 - Got rid of try..catch for filter validation

background.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 342 matching lines @@
     case "get-domain-enabled-state":
       // Returns whether this domain is in the exclusion list.
       // The browser action popup asks us this.
       if(sender.page)
       {
         sendResponse({enabled: !isPageWhitelisted(sender.page)});
         return;
       }
       break;
     case "add-filters":
-      var filters;
-      try
+      var result = parseFilters(msg.text);
+
+      if (result.error)
       {
-        filters = parseFilters(msg.text);
-      }
-      catch (error)
-      {
-        sendResponse({status: "invalid", error: error});
+        sendResponse({status: "invalid", error: result.error});
         break;
       }
 
-      for (var i = 0; i < filters.length; i++)
-        FilterStorage.addFilter(filters[i]);
+      for (var i = 0; i < result.filters.length; i++)
+        FilterStorage.addFilter(result.filters[i]);
 
       sendResponse({status: "ok"});
       break;
     case "add-subscription":
       ext.showOptions(function(page)
       {
         page.sendMessage(msg);
       });
       break;
     case "add-sitekey":
@@ skipping 31 matching lines @@
       break;
   }
 });
 
 // update icon when page changes location
 ext.pages.onLoading.addListener(function(page)
 {
   page.sendMessage({type: "clickhide-deactivate"});
   refreshIconAndContextMenu(page);
 });