replace NULL->nullptr in src/remoting.

remoting/signaling/iq_sender.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 "remoting/signaling/iq_sender.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 128 matching lines @@
 
 void IqRequest::CallCallback(const buzz::XmlElement* stanza) {
   if (!callback_.is_null()) {
     IqSender::ReplyCallback callback(callback_);
     callback_.Reset();
     callback.Run(this, stanza);
   }
 }
 
 void IqRequest::OnTimeout() {
-  CallCallback(NULL);
+  CallCallback(nullptr);
 }
 
 void IqRequest::OnResponse(const buzz::XmlElement* stanza) {
   // It's unsafe to delete signal strategy here, and the callback may
   // want to do that, so we post task to invoke the callback later.
   scoped_ptr<buzz::XmlElement> stanza_copy(new buzz::XmlElement(*stanza));
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE, base::Bind(&IqRequest::DeliverResponse, AsWeakPtr(),
                             base::Passed(&stanza_copy)));
 }
 
 void IqRequest::DeliverResponse(scoped_ptr<buzz::XmlElement> stanza) {
   CallCallback(stanza.get());
 }
 
 }  // namespace remoting