[Sync] Replacing NULL with nullptr/null throughout sync code.

chrome/browser/sync/sync_error_notifier_factory_ash.cc

Index: chrome/browser/sync/sync_error_notifier_factory_ash.cc
diff --git a/chrome/browser/sync/sync_error_notifier_factory_ash.cc b/chrome/browser/sync/sync_error_notifier_factory_ash.cc
index 6145c1590b54817b9f1998f942ab56f416d36833..2af253c951b8b3758583fa4e827367adf44722c8 100644
--- a/chrome/browser/sync/sync_error_notifier_factory_ash.cc
+++ b/chrome/browser/sync/sync_error_notifier_factory_ash.cc
@@ -36,19 +36,19 @@ SyncErrorNotifierFactory* SyncErrorNotifierFactory::GetInstance() {
 KeyedService* SyncErrorNotifierFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
   if (!ash::Shell::HasInstance())
-    return NULL;
+    return nullptr;
 
   Profile* profile = static_cast<Profile*>(context);
   browser_sync::ProfileSyncService* profile_sync_service =
       ProfileSyncServiceFactory::GetForProfile(profile);
 
   if (!profile_sync_service)
-    return NULL;
+    return nullptr;
 
   syncer::SyncErrorController* sync_error_controller =
       profile_sync_service->sync_error_controller();
   if (!sync_error_controller)
-    return NULL;
+    return nullptr;
 
   return new SyncErrorNotifier(sync_error_controller, profile);
 }