replace NULL->nullptr in src/remoting.

remoting/host/linux/x11_util.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/linux/x11_util.h"
 
 #include "base/bind.h"
 
 namespace remoting {
 
-static ScopedXErrorHandler* g_handler = NULL;
+static ScopedXErrorHandler* g_handler = nullptr;
 
 ScopedXErrorHandler::ScopedXErrorHandler(const Handler& handler):
     handler_(handler),
     ok_(true) {
   // This is a poor-man's check for incorrect usage. It doesn't handle the case
   // where a mix of ScopedXErrorHandler and raw XSetErrorHandler calls are used,
   // and it disallows nested ScopedXErrorHandlers on the same thread, despite
   // these being perfectly safe.
-  DCHECK(g_handler == NULL);
+  DCHECK(g_handler == nullptr);
   g_handler = this;
   previous_handler_ = XSetErrorHandler(HandleXErrors);
 }
 
 ScopedXErrorHandler::~ScopedXErrorHandler() {
-  g_handler = NULL;
+  g_handler = nullptr;
   XSetErrorHandler(previous_handler_);
 }
 
 namespace {
 void IgnoreXErrors(Display* display, XErrorEvent* error) {}
 }  // namespace
 
 // Static
 ScopedXErrorHandler::Handler ScopedXErrorHandler::Ignore() {
   return base::Bind(IgnoreXErrors);
 }
 
 int ScopedXErrorHandler::HandleXErrors(Display* display, XErrorEvent* error) {
-  DCHECK(g_handler != NULL);
+  DCHECK(g_handler != nullptr);
   g_handler->ok_ = false;
   g_handler->handler_.Run(display, error);
   return 0;
 }
 
 
 ScopedXGrabServer::ScopedXGrabServer(Display* display)
     : display_(display) {
   XGrabServer(display_);
 }
 
 ScopedXGrabServer::~ScopedXGrabServer() {
   XUngrabServer(display_);
   XFlush(display_);
 }
 
 }  // namespace remoting