Show a warning to people having a corrupted file storage

lib/adblockplus_compat.js

 /*
  * This file is part of the Adblock Plus extension,
  * Copyright (C) 2006-2012 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 136 matching lines @@
       return new FakeFile(path);
     },
 
     readFromFile: function(file, decode, listener, callback, timeLineID)
     {
       if ("spec" in file && /^defaults\b/.test(file.spec))
       {
         // Code attempts to read the default patterns.ini, we don't have that.
         // Make sure to execute first-run actions instead.
         callback(null);
+        if (localStorage.currentVersion)
+          seenDataCorruption = true;
         delete localStorage.currentVersion;
         require("filterNotifier").FilterNotifier.triggerListeners("load");
         return;
       }
 
       this._getFileEntry(file, false, function(fs, fileEntry)
       {
         fileEntry.file(function(file)
         {
           var reader = new FileReader();
@@ skipping 424 matching lines @@
   status: -1,
   notificationCallbacks: {},
   loadFlags: 0,
   INHIBIT_CACHING: 0,
   VALIDATE_ALWAYS: 0,
   QueryInterface: function()
   {
     return this;
   }
 };