[Sync] Replacing NULL with nullptr in code and null in comments for components/sync/

components/sync/base/sync_prefs.h

 // Copyright (c) 2012 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 COMPONENTS_SYNC_BASE_SYNC_PREFS_H_
 #define COMPONENTS_SYNC_BASE_SYNC_PREFS_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 39 matching lines @@
 //
 //   profile_sync_service_startup_unittest.cc
 //   profile_sync_service.cc
 //   sync_setup_flow.cc
 //   sync_setup_wizard.cc
 //   sync_setup_wizard_unittest.cc
 //   two_client_preferences_sync_test.cc
 class SyncPrefs : NON_EXPORTED_BASE(public base::NonThreadSafe),
                   public base::SupportsWeakPtr<SyncPrefs> {
  public:
-  // |pref_service| may not be NULL.
+  // |pref_service| may not be null.
   // Does not take ownership of |pref_service|.
   explicit SyncPrefs(PrefService* pref_service);
 
   // For testing.
   SyncPrefs();
 
   virtual ~SyncPrefs();
 
   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
@@ skipping 120 matching lines @@
   bool GetDataTypePreferred(ModelType type) const;
   void SetDataTypePreferred(ModelType type, bool is_preferred);
 
   // Returns a ModelTypeSet based on |types| expanded to include pref groups
   // (see |pref_groups_|), but as a subset of |registered_types|.
   ModelTypeSet ResolvePrefGroups(ModelTypeSet registered_types,
                                  ModelTypeSet types) const;
 
   void OnSyncManagedPrefChanged();
 
-  // May be NULL.
+  // May be null.
   PrefService* const pref_service_;
 
   base::ObserverList<SyncPrefObserver> sync_pref_observers_;
 
   // The preference that controls whether sync is under control by
   // configuration management.
   BooleanPrefMember pref_sync_managed_;
 
   // Groups of prefs that always have the same value as a "master" pref.
   // For example, the APPS group has {APP_NOTIFICATIONS, APP_SETTINGS}
   // (as well as APPS, but that is implied), so
   //   pref_groups_[APPS] =       { APP_NOTIFICATIONS,
   //                                          APP_SETTINGS }
   //   pref_groups_[EXTENSIONS] = { EXTENSION_SETTINGS }
   // etc.
   typedef std::map<ModelType, ModelTypeSet> PrefGroupsMap;
   PrefGroupsMap pref_groups_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncPrefs);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_BASE_SYNC_PREFS_H_