Move handling of dialog preferences to Preferences class

chrome/browser/resources/options/import_data_overlay.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.define('options', function() {
   var OptionsPage = options.OptionsPage;
 
   /**
    * ImportDataOverlay class
    * Encapsulated handling of the 'Import Data' overlay page.
@@ skipping 146 matching lines @@
      * checkbox goes back to the default "checked" state (or alternatively, to
      * the state set by a recommended policy).
      * @private
      */
     clearUserPrefs_: function() {
       var importPrefs = ['import_history',
                          'import_bookmarks',
                          'import_saved_passwords',
                          'import_search_engine'];
       for (var i = 0; i < importPrefs.length; i++)
-        Preferences.clearPref(importPrefs[i], undefined);
+        Preferences.clearPref(importPrefs[i], true);
     },
 
     /**
      * Update the dialog layout to reflect success state.
      * @param {boolean} success If true, show success dialog elements.
      * @private
      */
     updateSuccessState_: function(success) {
       var sections = document.querySelectorAll('.import-data-configure');
       for (var i = 0; i < sections.length; i++)
@@ skipping 60 matching lines @@
     ImportDataOverlay.getInstance().updateSuccessState_(false);
 
     OptionsPage.navigateToPage('importData');
   };
 
   // Export
   return {
     ImportDataOverlay: ImportDataOverlay
   };
 });