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

chrome/browser/sync/sessions/notification_service_sessions_router.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/sync/sessions/notification_service_sessions_router.h"
 
 #include "base/logging.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/history/history_service_factory.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 43 matching lines @@
   return delegate;
 #endif
 }
 
 }  // namespace
 
 NotificationServiceSessionsRouter::NotificationServiceSessionsRouter(
     Profile* profile,
     SyncSessionsClient* sessions_client,
     const syncer::SyncableService::StartSyncFlare& flare)
-    : handler_(NULL),
+    : handler_(nullptr),
       profile_(profile),
       sessions_client_(sessions_client),
       flare_(flare),
       weak_ptr_factory_(this) {
   registrar_.Add(this, chrome::NOTIFICATION_TAB_PARENTED,
       content::NotificationService::AllSources());
   registrar_.Add(this, content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
       content::NotificationService::AllSources());
   registrar_.Add(this, content::NOTIFICATION_NAV_LIST_PRUNED,
       content::NotificationService::AllSources());
@@ skipping 125 matching lines @@
 }
 
 void NotificationServiceSessionsRouter::StartRoutingTo(
     LocalSessionEventHandler* handler) {
   DCHECK(!handler_);
   handler_ = handler;
 }
 
 void NotificationServiceSessionsRouter::Stop() {
   weak_ptr_factory_.InvalidateWeakPtrs();
-  handler_ = NULL;
+  handler_ = nullptr;
 }
 
 }  // namespace sync_sessions