replace NULL->nullptr in src/remoting.

remoting/host/linux/x_server_clipboard.cc

 // Copyright (c) 2012 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/linux/x_server_clipboard.h"
 
 #include <X11/extensions/Xfixes.h>
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "remoting/base/constants.h"
 #include "remoting/base/logging.h"
 #include "remoting/base/util.h"
 
 namespace remoting {
 
 XServerClipboard::XServerClipboard()
-    : display_(NULL),
+    : display_(nullptr),
       clipboard_window_(BadValue),
       xfixes_event_base_(-1),
       clipboard_atom_(None),
       large_selection_atom_(None),
       selection_string_atom_(None),
       targets_atom_(None),
       timestamp_atom_(None),
       utf8_string_atom_(None),
       large_selection_property_(None) {
 }
@@ skipping 337 matching lines @@
   } else {
     LOG(ERROR) << "XSetSelectionOwner failed for selection " << selection;
   }
 }
 
 bool XServerClipboard::IsSelectionOwner(Atom selection) {
   return selections_owned_.find(selection) != selections_owned_.end();
 }
 
 }  // namespace remoting