replace NULL->nullptr in src/remoting.

remoting/host/fake_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/fake_desktop_capturer.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
@@ skipping 103 matching lines @@
     frame->mutable_updated_region()->AddRect(webrtc::DesktopRect::MakeXYWH(
         box_pos_x_, box_pos_y_, kBoxWidth, kBoxHeight));
   }
 
   return frame.Pass();
 }
 
 }  // namespace
 
 FakeDesktopCapturer::FakeDesktopCapturer()
-    : callback_(NULL) {
+    : callback_(nullptr) {
   frame_generator_ = base::Bind(&DefaultFrameGenerator::GenerateFrame,
                                 new DefaultFrameGenerator());
 }
 
 FakeDesktopCapturer::~FakeDesktopCapturer() {}
 
 void FakeDesktopCapturer::set_frame_generator(
     const FrameGenerator& frame_generator) {
   DCHECK(!callback_);
   frame_generator_ = frame_generator;
 }
 
 void FakeDesktopCapturer::Start(Callback* callback) {
   DCHECK(!callback_);
   DCHECK(callback);
   callback_ = callback;
 }
 
 void FakeDesktopCapturer::Capture(const webrtc::DesktopRegion& region) {
   base::Time capture_start_time = base::Time::Now();
   scoped_ptr<webrtc::DesktopFrame> frame = frame_generator_.Run(callback_);
   frame->set_capture_time_ms(
       (base::Time::Now() - capture_start_time).InMillisecondsRoundedUp());
   callback_->OnCaptureCompleted(frame.release());
 }
 
 }  // namespace remoting