Use PrefChangeRegistrar everywhere

chrome/browser/dom_ui/shown_sections_handler.cc

 // Copyright (c) 2010 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/dom_ui/shown_sections_handler.h"
 
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/string_number_conversions.h"
 #include "base/values.h"
@@ skipping 30 matching lines @@
 
 }  // namespace
 
 // static
 int ShownSectionsHandler::GetShownSections(PrefService* prefs) {
   return prefs->GetInteger(prefs::kNTPShownSections);
 }
 
 ShownSectionsHandler::ShownSectionsHandler(PrefService* pref_service)
     : pref_service_(pref_service) {
-  pref_service_->AddPrefObserver(prefs::kNTPShownSections, this);
-}
-
-ShownSectionsHandler::~ShownSectionsHandler() {
-  pref_service_->RemovePrefObserver(prefs::kNTPShownSections, this);
+  registrar_.Init(pref_service);
+  registrar_.Add(prefs::kNTPShownSections, this);
 }
 
 void ShownSectionsHandler::RegisterMessages() {
   dom_ui_->RegisterMessageCallback("getShownSections",
       NewCallback(this, &ShownSectionsHandler::HandleGetShownSections));
   dom_ui_->RegisterMessageCallback("setShownSections",
       NewCallback(this, &ShownSectionsHandler::HandleSetShownSections));
 }
 
 void ShownSectionsHandler::Observe(NotificationType type,
@@ skipping 45 matching lines @@
       shown_sections = APPS;
     else
       shown_sections = THUMB;
 
     changed = true;
   }
 
   if (changed)
     pref_service->SetInteger(prefs::kNTPShownSections, shown_sections);
 }