replace NULL->nullptr in src/remoting.

remoting/protocol/clipboard_filter.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 "base/logging.h"
 #include "remoting/protocol/clipboard_filter.h"
 
 namespace remoting {
 namespace protocol {
 
-ClipboardFilter::ClipboardFilter() : clipboard_stub_(NULL), enabled_(true) {
+ClipboardFilter::ClipboardFilter() : clipboard_stub_(nullptr), enabled_(true) {
 }
 
 ClipboardFilter::ClipboardFilter(ClipboardStub* clipboard_stub)
     : clipboard_stub_(clipboard_stub), enabled_(true) {
 }
 
 ClipboardFilter::~ClipboardFilter() {
 }
 
 void ClipboardFilter::set_clipboard_stub(ClipboardStub* clipboard_stub) {
   clipboard_stub_ = clipboard_stub;
 }
 
 void ClipboardFilter::InjectClipboardEvent(const ClipboardEvent& event) {
-  if (enabled_ && clipboard_stub_ != NULL)
+  if (enabled_ && clipboard_stub_ != nullptr)
     clipboard_stub_->InjectClipboardEvent(event);
 }
 
 }  // namespace protocol
 }  // namespace remoting