replace NULL->nullptr in src/remoting.

remoting/host/win/window_station_and_desktop.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/win/window_station_and_desktop.h"
 
 #include <algorithm>
 
 namespace remoting {
 
 WindowStationAndDesktop::WindowStationAndDesktop()
-    : desktop_(NULL),
-      window_station_(NULL) {
+    : desktop_(nullptr),
+      window_station_(nullptr) {
 }
 
 WindowStationAndDesktop::~WindowStationAndDesktop() {
-  SetDesktop(NULL);
-  SetWindowStation(NULL);
+  SetDesktop(nullptr);
+  SetWindowStation(nullptr);
 }
 
 void WindowStationAndDesktop::SetDesktop(HDESK desktop) {
   std::swap(desktop_, desktop);
   if (desktop)
     CloseDesktop(desktop);
 }
 
 void WindowStationAndDesktop::SetWindowStation(HWINSTA window_station) {
   std::swap(window_station_, window_station);
   if (window_station)
     CloseWindowStation(window_station);
 }
 
 void WindowStationAndDesktop::Swap(WindowStationAndDesktop& other) {
   std::swap(desktop_, other.desktop_);
   std::swap(window_station_, other.window_station_);
 }
 
 }  // namespace remoting