replace NULL->nullptr in src/remoting.

remoting/host/chromeos/skia_bitmap_desktop_frame.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 "base/logging.h"
 #include "remoting/host/chromeos/skia_bitmap_desktop_frame.h"
 
 namespace remoting {
 
 // static
@@ skipping 11 matching lines @@
   SkiaBitmapDesktopFrame* result = new SkiaBitmapDesktopFrame(
       size, bitmap->rowBytes(), bitmap_data, bitmap.Pass());
 
   return result;
 }
 
 SkiaBitmapDesktopFrame::SkiaBitmapDesktopFrame(webrtc::DesktopSize size,
                                                int stride,
                                                uint8_t* data,
                                                scoped_ptr<SkBitmap> bitmap)
-    : DesktopFrame(size, stride, data, NULL), bitmap_(bitmap.Pass()) {
+    : DesktopFrame(size, stride, data, nullptr), bitmap_(bitmap.Pass()) {
 }
 
 SkiaBitmapDesktopFrame::~SkiaBitmapDesktopFrame() {
 }
 
-}  // namespace remoting
+}  // namespace remoting