replace NULL->nullptr in src/remoting.

remoting/protocol/name_value_map.h

 // 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.
 //
 // Helper functions that allow to map enum values to strings.
 
 #include <stddef.h>
 
 #include "base/logging.h"
 
 namespace remoting {
 namespace protocol {
 
 template <typename T>
 struct NameMapElement {
   const T value;
   const char* const name;
 };
 
 template <typename T, size_t N>
 const char* ValueToName(const NameMapElement<T> (&map)[N], T value) {
   for (size_t i = 0; i < N; ++i) {
     if (map[i].value == value)
       return map[i].name;
   }
   NOTREACHED();
-  return NULL;
+  return nullptr;
 }
 
 template <typename T, size_t N>
 bool NameToValue(const NameMapElement<T> (&map)[N],
                  const std::string& name,
                  T* result) {
   for (size_t i = 0; i < N; ++i) {
     if (map[i].name == name) {
       *result = map[i].value;
       return true;
     }
   }
   return false;
 }
 
 }  // namespace protocol
 }  // namespace remoting