Dynamically update sign-in/Sync status in the profile creation overlay.

chrome/browser/resources/options/manage_profile_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;
   var ArrayDataModel = cr.ui.ArrayDataModel;
 
   /**
    * ManageProfileOverlay class
@@ skipping 599 matching lines @@
      * @param {boolean} hasError Whether the user's sign-in credentials are
      *     still valid.
      * @private
      */
     updateSignedInStatus_: function(email, hasError) {
       this.signedInEmail_ = email;
       this.hasError_ = hasError;
       var isSignedIn = email !== '';
       $('create-profile-managed-signed-in').hidden = !isSignedIn;
       $('create-profile-managed-not-signed-in').hidden = isSignedIn;
-      $('select-existing-managed-profile-checkbox').hidden = !isSignedIn;
-      $('choose-existing-managed-profile').hidden = !isSignedIn;
+      var hideSelectExistingManagedUsers =
+          !isSignedIn ||
+          !loadTimeData.getBoolean('allowCreateExistingManagedUsers');
+      $('select-existing-managed-profile-checkbox').hidden =
+          hideSelectExistingManagedUsers;
+      $('choose-existing-managed-profile').hidden =
+          hideSelectExistingManagedUsers;
 
       if (isSignedIn) {
         var accountDetailsOutOfDate =
             $('create-profile-managed-account-details-out-of-date-label');
         accountDetailsOutOfDate.textContent = loadTimeData.getStringF(
             'manageProfilesManagedAccountDetailsOutOfDate', email);
         accountDetailsOutOfDate.hidden = !hasError;
 
         $('create-profile-managed-signed-in-label').textContent =
             loadTimeData.getStringF(
@@ skipping 82 matching lines @@
       return instance[name + '_'].apply(instance, arguments);
     };
   });
 
   // Export
   return {
     ManageProfileOverlay: ManageProfileOverlay,
     CreateProfileOverlay: CreateProfileOverlay,
   };
 });