MD User Manager: Display error message when all profiles are locked.

chrome/test/data/webui/md_user_manager/test_profile_browser_proxy.js

 // Copyright 2016 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.
 
 /**
  * The mock signin.ProfileBrowserProxy.
  *
  * @constructor
  * @implements {signin.ProfileBrowserProxy}
  * @extends {settings.TestBrowserProxy}
  */
 var TestProfileBrowserProxy = function() {
   settings.TestBrowserProxy.call(this, [
     'getAvailableIcons',
     'getSignedInUsers',
     'launchGuestUser',
     'createProfile',
     'cancelCreateProfile',
     'initializeUserManager',
     'launchUser',
     'getExistingSupervisedUsers',
+    'areAllProfilesLocked',
   ]);
 
   /** @private {!Array<string>} */
   this.iconUrls_ = [];
 
   /** @private {!Array<SignedInUser>} */
   this.signedInUsers_ = [];
 
   /** @private {!ProfileInfo} */
   this.defaultProfileInfo_ = {};
@@ skipping 71 matching lines @@
   /** @override */
   launchGuestUser: function() {
     this.methodCalled('launchGuestUser');
   },
 
   /** @override */
   getExistingSupervisedUsers: function() {
     this.methodCalled('getExistingSupervisedUsers');
     return Promise.resolve(this.existingSupervisedUsers_);
   },
+
+  /** @override */
+  areAllProfilesLocked: function() {
+    this.methodCalled('areAllProfilesLocked');
+    return Promise.resolve(false);
+  },
 };