replace NULL->nullptr in src/remoting.

remoting/protocol/it2me_host_authenticator_factory.cc

 // 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.
 
 #include "remoting/protocol/it2me_host_authenticator_factory.h"
 
 #include "base/logging.h"
 #include "remoting/base/rsa_key_pair.h"
 #include "remoting/protocol/negotiating_host_authenticator.h"
 
@@ skipping 10 matching lines @@
 }
 
 It2MeHostAuthenticatorFactory::~It2MeHostAuthenticatorFactory() {
 }
 
 scoped_ptr<Authenticator> It2MeHostAuthenticatorFactory::CreateAuthenticator(
     const std::string& local_jid,
     const std::string& remote_jid,
     const buzz::XmlElement* first_message) {
   return NegotiatingHostAuthenticator::CreateWithSharedSecret(
-      local_cert_, key_pair_, shared_secret_, AuthenticationMethod::NONE, NULL);
+      local_cert_, key_pair_, shared_secret_, AuthenticationMethod::NONE,
+      nullptr);
 }
 
 }  // namespace protocol
 }  // namespace remoting