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

chrome/browser/sync/sync_error_notifier_ash.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/sync_error_notifier_ash.h"
 
 #include "ash/common/system/system_notifier.h"
 #include "base/strings/utf_string_conversions.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
@@ skipping 96 matching lines @@
   OnErrorChanged();
 }
 
 SyncErrorNotifier::~SyncErrorNotifier() {
   DCHECK(!error_controller_)
       << "SyncErrorNotifier::Shutdown() was not called";
 }
 
 void SyncErrorNotifier::Shutdown() {
   error_controller_->RemoveObserver(this);
-  error_controller_ = NULL;
+  error_controller_ = nullptr;
 }
 
 void SyncErrorNotifier::OnErrorChanged() {
   NotificationUIManager* notification_ui_manager =
       g_browser_process->notification_ui_manager();
 
-  // notification_ui_manager() may return NULL when shutting down.
+  // notification_ui_manager() may return null when shutting down.
   if (!notification_ui_manager)
     return;
 
   if (!error_controller_->HasError()) {
     g_browser_process->notification_ui_manager()->CancelById(
         notification_id_, NotificationUIManager::GetProfileID(profile_));
     return;
   }
 
 #if defined(OS_CHROMEOS)
@@ skipping 36 matching lines @@
       message_center::NOTIFICATION_TYPE_SIMPLE,
       l10n_util::GetStringUTF16(IDS_SYNC_ERROR_BUBBLE_VIEW_TITLE),
       l10n_util::GetStringUTF16(IDS_SYNC_PASSPHRASE_ERROR_BUBBLE_VIEW_MESSAGE),
       ui::ResourceBundle::GetSharedInstance().GetImageNamed(
           IDR_NOTIFICATION_ALERT),
       notifier_id,
       base::string16(),  // display_source
       GURL(notification_id_), notification_id_, data, delegate);
   notification_ui_manager->Add(notification, profile_);
 }