replace NULL->nullptr in src/remoting.

remoting/host/setup/test_util.cc

 // Copyright 2013 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/setup/test_util.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #elif defined(OS_POSIX)
 #include <unistd.h>
 #endif
 
 namespace remoting {
 
 bool MakePipe(base::File* read_file,
               base::File* write_file) {
 #if defined(OS_WIN)
   base::PlatformFile read_handle;
   base::PlatformFile write_handle;
-  if (!CreatePipe(&read_handle, &write_handle, NULL, 0))
+  if (!CreatePipe(&read_handle, &write_handle, nullptr, 0))
     return false;
   *read_file = base::File(read_handle);
   *write_file = base::File(write_handle);
   return true;
 #elif defined(OS_POSIX)
   int fds[2];
   if (pipe(fds) == 0) {
     *read_file = base::File(fds[0]);
     *write_file = base::File(fds[1]);
     return true;
   }
   return false;
 #else
 #error Not implemented
 #endif
 }
 
 }  // namepsace remoting