NULL -> nullptr under athena/

athena/extensions/extensions_delegate.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 "athena/extensions/public/extensions_delegate.h"
 
 #include "base/logging.h"
 
 namespace athena {
 namespace {
 
-ExtensionsDelegate* instance = NULL;
+ExtensionsDelegate* instance = nullptr;
 
 }  // namespace
 
 ExtensionsDelegate::ExtensionsDelegate() {
   DCHECK(!instance);
   instance = this;
 }
 
 ExtensionsDelegate::~ExtensionsDelegate() {
   DCHECK(instance);
-  instance = NULL;
+  instance = nullptr;
 }
 
 // static
 ExtensionsDelegate* ExtensionsDelegate::Get(content::BrowserContext* context) {
   DCHECK(instance);
   DCHECK_EQ(context, instance->GetBrowserContext());
   return instance;
 }
 
 // static
 void ExtensionsDelegate::Shutdown() {
   DCHECK(instance);
   delete instance;
 }
 
 }  // namespace athena