MD Settings: fix crash from strongly bound handler that goes away

chrome/browser/ui/webui/settings/profile_info_handler.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_SETTINGS_PROFILE_INFO_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SETTINGS_PROFILE_INFO_HANDLER_H_
 
 #include <memory>
 
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "base/scoped_observer.h"
 #include "build/build_config.h"
 #include "chrome/browser/profiles/profile_attributes_storage.h"
 #include "chrome/browser/ui/webui/settings/settings_page_ui_handler.h"
 #include "components/prefs/pref_change_registrar.h"
 
 #if defined(OS_CHROMEOS)
 #include "components/user_manager/user_manager.h"
 #else
 #include "chrome/browser/profiles/profile_statistics_common.h"
@@ skipping 67 matching lines @@
   ScopedObserver<user_manager::UserManager, ProfileInfoHandler>
       user_manager_observer_;
 #endif
 
   ScopedObserver<ProfileAttributesStorage, ProfileInfoHandler>
       profile_observer_;
 
   // Used to listen for changes in the list of managed supervised users.
   PrefChangeRegistrar profile_pref_registrar_;
 
+  base::WeakPtrFactory<ProfileInfoHandler> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(ProfileInfoHandler);
 };
 
 }  // namespace settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_PROFILE_INFO_HANDLER_H_