options: fix "Import" button for idle options pages.

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 Page = cr.ui.pageManager.Page;
   var PageManager = cr.ui.pageManager.PageManager;
 
   /**
    * ImportDataOverlay class
@@ skipping 14 matching lines @@
     __proto__: Page.prototype,
 
     /** @override */
     initializePage: function() {
       Page.prototype.initializePage.call(this);
 
       var self = this;
       var checkboxes =
           document.querySelectorAll('#import-checkboxes input[type=checkbox]');
       for (var i = 0; i < checkboxes.length; i++) {
-        checkboxes[i].onchange = function() {
+        checkboxes[i].customPrefChangeHandler = function(e) {
+          options.PrefCheckbox.prototype.defaultPrefChangeHandler.call(this, e);
           self.validateCommitButton_();
+          return true;
         };
       }
 
       $('import-browsers').onchange = function() {
         self.updateCheckboxes_();
         self.validateCommitButton_();
         self.updateBottomBar_();
       };
 
       $('import-data-commit').onclick = function() {
@@ skipping 223 matching lines @@
     ImportDataOverlay.getInstance().validateCommitButton_();
 
     PageManager.showPageByName('importData');
   };
 
   // Export
   return {
     ImportDataOverlay: ImportDataOverlay
   };
 });