Use ScopedObserver to observe the SupervisedUserSyncService in SupervisedUserImportHandler.

chrome/browser/ui/webui/options/supervised_user_import_handler.cc

 // 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.
 
 #include "chrome/browser/ui/webui/options/supervised_user_import_handler.h"
 
 #include <set>
 
 #include "base/bind.h"
 #include "base/prefs/pref_service.h"
@@ skipping 38 matching lines @@
   return cache.ProfileIsLegacySupervisedAtIndex(index);
 }
 
 }  // namespace
 
 namespace options {
 
 SupervisedUserImportHandler::SupervisedUserImportHandler()
     : profile_observer_(this),
       signin_error_observer_(this),
+      supervised_user_sync_service_observer_(this),
       removed_profile_is_supervised_(false),
       weak_ptr_factory_(this) {
 }
 
 SupervisedUserImportHandler::~SupervisedUserImportHandler() {
-  Profile* profile = Profile::FromWebUI(web_ui());
-  if (!profile->IsSupervised()) {
-    SupervisedUserSyncService* service =
-        SupervisedUserSyncServiceFactory::GetForProfile(profile);
-    if (service)
-      service->RemoveObserver(this);
-    subscription_.reset();
-  }
 }
 
 void SupervisedUserImportHandler::GetLocalizedValues(
     base::DictionaryValue* localized_strings) {
   DCHECK(localized_strings);
 
   static OptionsStringResource resources[] = {
       { "supervisedUserImportTitle",
           IDS_IMPORT_EXISTING_SUPERVISED_USER_TITLE },
       { "supervisedUserImportText", IDS_IMPORT_EXISTING_SUPERVISED_USER_TEXT },
@@ skipping 16 matching lines @@
 }
 
 void SupervisedUserImportHandler::InitializeHandler() {
   Profile* profile = Profile::FromWebUI(web_ui());
   if (!profile->IsSupervised()) {
     profile_observer_.Add(
         &g_browser_process->profile_manager()->GetProfileInfoCache());
     SupervisedUserSyncService* sync_service =
         SupervisedUserSyncServiceFactory::GetForProfile(profile);
     if (sync_service) {
-      sync_service->AddObserver(this);
+      supervised_user_sync_service_observer_.Add(sync_service);
       signin_error_observer_.Add(
           SigninErrorControllerFactory::GetForProfile(profile));
       SupervisedUserSharedSettingsService* settings_service =
           SupervisedUserSharedSettingsServiceFactory::GetForBrowserContext(
               profile);
       subscription_ = settings_service->Subscribe(
           base::Bind(&SupervisedUserImportHandler::OnSharedSettingChanged,
                      weak_ptr_factory_.GetWeakPtr()));
     } else {
       DCHECK(!SupervisedUserSharedSettingsServiceFactory::GetForBrowserContext(
@@ skipping 163 matching lines @@
     const std::string& key) {
   if (key == supervised_users::kChromeAvatarIndex)
     FetchSupervisedUsers();
 }
 
 void SupervisedUserImportHandler::OnErrorChanged() {
   FetchSupervisedUsers();
 }
 
 }  // namespace options