replace NULL->nullptr in src/remoting.

remoting/host/host_extension_session_manager.cc

 // Copyright 2014 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/host_extension_session_manager.h"
 
 #include "remoting/base/capabilities.h"
 #include "remoting/codec/video_encoder.h"
 #include "remoting/host/client_session_control.h"
 #include "remoting/host/host_extension.h"
 #include "remoting/host/host_extension_session.h"
 #include "third_party/webrtc/modules/desktop_capture/desktop_capturer.h"
 namespace remoting {
 
 HostExtensionSessionManager::HostExtensionSessionManager(
     const std::vector<HostExtension*>& extensions,
     ClientSessionControl* client_session_control)
     : client_session_control_(client_session_control),
-      client_stub_(NULL),
+      client_stub_(nullptr),
       extensions_(extensions) {
 }
 
 HostExtensionSessionManager::~HostExtensionSessionManager() {
 }
 
 std::string HostExtensionSessionManager::GetCapabilities() const {
   std::string capabilities;
   for (HostExtensions::const_iterator extension = extensions_.begin();
        extension != extensions_.end(); ++extension) {
@@ skipping 72 matching lines @@
       it != extension_sessions_.end(); ++it) {
     if ((*it)->OnExtensionMessage(
             client_session_control_, client_stub_, message)) {
       return true;
     }
   }
   return false;
 }
 
 }  // namespace remoting