replace NULL->nullptr in src/remoting.

remoting/host/win/rdp_desktop_session.cc

 // Copyright (c) 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/win/rdp_desktop_session.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "remoting/base/auto_thread_task_runner.h"
 #include "remoting/host/win/chromoting_module.h"
 #include "third_party/webrtc/modules/desktop_capture/desktop_geometry.h"
@@ skipping 15 matching lines @@
   DCHECK(task_runner->BelongsToCurrentThread());
 
   client_.reset(new RdpClient(task_runner, task_runner,
                               webrtc::DesktopSize(width, height),
                               base::UTF16ToUTF8(terminal_id), this));
   return S_OK;
 }
 
 STDMETHODIMP RdpDesktopSession::Disconnect() {
   client_.reset();
-  event_handler_ = NULL;
+  event_handler_ = nullptr;
   return S_OK;
 }
 
 STDMETHODIMP RdpDesktopSession::ChangeResolution(long width, long height) {
   return E_NOTIMPL;
 }
 
 STDMETHODIMP RdpDesktopSession::InjectSas() {
   if (client_)
     client_->InjectSas();
   return S_OK;
 }
 
 void RdpDesktopSession::OnRdpConnected() {
   HRESULT result = event_handler_->OnRdpConnected();
   CHECK(SUCCEEDED(result)) << "OnRdpConnected() failed: 0x"
                            << std::hex << result << std::dec << ".";
 }
 
 void RdpDesktopSession::OnRdpClosed() {
   HRESULT result = event_handler_->OnRdpClosed();
   CHECK(SUCCEEDED(result)) << "OnRdpClosed() failed: 0x" << std::hex << result
                            << std::dec << ".";
 }
 
 } // namespace remoting