replace NULL->nullptr in src/remoting.

remoting/host/dns_blackhole_checker.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/host/dns_blackhole_checker.h"
 
 #include "net/url_request/url_fetcher.h"
 #include "net/url_request/url_request_context_getter.h"
 #include "remoting/base/logging.h"
 #include "url/gurl.h"
@@ skipping 21 matching lines @@
 // CheckStatus().
 void DnsBlackholeChecker::OnURLFetchComplete(const net::URLFetcher* source) {
   int response = source->GetResponseCode();
   bool allow = false;
   if (source->GetResponseCode() == 200) {
     HOST_LOG << "Successfully connected to host talkgadget.";
     allow = true;
   } else {
     HOST_LOG << "Unable to connect to host talkgadget (" << response << ")";
   }
-  url_fetcher_.reset(NULL);
+  url_fetcher_.reset(nullptr);
   callback_.Run(allow);
   callback_.Reset();
 }
 
 void DnsBlackholeChecker::CheckForDnsBlackhole(
     const base::Callback<void(bool)>& callback) {
   // Make sure we're not currently in the middle of a connection check.
   if (!url_fetcher_.get()) {
     DCHECK(callback_.is_null());
     callback_ = callback;
     std::string talkgadget_url("https://");
     if (talkgadget_prefix_.empty()) {
       talkgadget_url += kDefaultHostTalkGadgetPrefix;
     } else {
       talkgadget_url += talkgadget_prefix_;
     }
     talkgadget_url += kTalkGadgetUrl;
     HOST_LOG << "Verifying connection to " << talkgadget_url;
     url_fetcher_.reset(net::URLFetcher::Create(GURL(talkgadget_url),
                                                net::URLFetcher::GET, this));
     url_fetcher_->SetRequestContext(url_request_context_getter_.get());
     url_fetcher_->Start();
   } else {
     HOST_LOG << "Pending connection check";
   }
 }
 
 }  // namespace remoting