replace NULL->nullptr in src/remoting.

remoting/host/chromeos/aura_desktop_capturer.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/chromeos/aura_desktop_capturer.h"
 
 #include "base/bind.h"
 #include "cc/output/copy_output_request.h"
 #include "cc/output/copy_output_result.h"
 #include "remoting/host/chromeos/skia_bitmap_desktop_frame.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_tree_host.h"
 
 #if defined(USE_ASH)
 #include "ash/shell.h"
 #endif
 
 namespace remoting {
 
 AuraDesktopCapturer::AuraDesktopCapturer()
-    : callback_(NULL), desktop_window_(NULL), weak_factory_(this) {
+    : callback_(nullptr), desktop_window_(nullptr), weak_factory_(this) {
 }
 
 AuraDesktopCapturer::~AuraDesktopCapturer() {
 }
 
 void AuraDesktopCapturer::Start(webrtc::DesktopCapturer::Callback* callback) {
 #if defined(USE_ASH)
   if (ash::Shell::HasInstance()) {
     // TODO(kelvinp): Use ash::Shell::GetAllRootWindows() when multiple monitor
     // support is implemented.
@@ skipping 34 matching lines @@
       frame->size().width(), frame->size().height());
 
   // TODO(kelvinp): Set Frame DPI according to the screen resolution.
   // See cc::Layer::contents_scale_(x|y)() and frame->set_depi().
   frame->mutable_updated_region()->SetRect(rect);
 
   callback_->OnCaptureCompleted(frame.release());
 }
 
 }  // namespace remoting