Clean up FtpTransactionFacory ownership.

net/ftp/ftp_network_layer.cc

 // Copyright (c) 2008 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 "net/ftp/ftp_network_layer.h"
 
+#include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "net/ftp/ftp_network_session.h"
 #include "net/ftp/ftp_network_transaction.h"
 #include "net/socket/client_socket_factory.h"
 
 namespace net {
 
 FtpNetworkLayer::FtpNetworkLayer(HostResolver* host_resolver)
     : session_(new FtpNetworkSession(host_resolver)),
       suspended_(false) {
+  DCHECK(host_resolver);
 }
 
 FtpNetworkLayer::~FtpNetworkLayer() {
 }
 
 std::unique_ptr<FtpTransaction> FtpNetworkLayer::CreateTransaction() {
   if (suspended_)
     return std::unique_ptr<FtpTransaction>();
 
   return base::MakeUnique<FtpNetworkTransaction>(
       session_->host_resolver(), ClientSocketFactory::GetDefaultFactory());
 }
 
 void FtpNetworkLayer::Suspend(bool suspend) {
   suspended_ = suspend;
 }
 
 }  // namespace net