Update the AvatarMenu when a supervised user's custodian info changes.

chrome/browser/supervised_user/supervised_user_service_observer.h

 // Copyright 2014 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.
 
 #ifndef CHROME_BROWSER_SUPERVISED_USER_SUPERVISED_USER_SERVICE_OBSERVER_H_
 #define CHROME_BROWSER_SUPERVISED_USER_SUPERVISED_USER_SERVICE_OBSERVER_H_
 
 class SupervisedUserServiceObserver {
  public:
   // Called whenever the URL filter is updated, e.g. a manual exception or a
   // content pack is added, or the default fallback behavior is changed.
   virtual void OnURLFilterChanged() {}
 
+  // Called when information about the supervised user's custodian is changed,
+  // e.g. the display name.
+  virtual void OnCustodianInfoChanged() {}
+
  protected:
   virtual ~SupervisedUserServiceObserver() {}
 };
 
 #endif  // CHROME_BROWSER_SUPERVISED_USER_SUPERVISED_USER_SERVICE_OBSERVER_H_