replace NULL->nullptr in src/remoting.

remoting/host/win/security_descriptor.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.
 
 #ifndef REMOTING_HOST_WIN_SECURITY_DESCRIPTOR_H_
 #define REMOTING_HOST_WIN_SECURITY_DESCRIPTOR_H_
 
 #include <windows.h>
 
 #include <string>
 
 #include "remoting/base/typed_buffer.h"
 
 namespace remoting {
 
 typedef TypedBuffer<ACL> ScopedAcl;
 typedef TypedBuffer<SECURITY_DESCRIPTOR> ScopedSd;
 typedef TypedBuffer<SID> ScopedSid;
 
 // Converts an SDDL string into a binary self-relative security descriptor.
 ScopedSd ConvertSddlToSd(const std::string& sddl);
 
 // Converts a SID into a text string.
 std::string ConvertSidToString(SID* sid);
 
-// Returns the logon SID of a token. Returns NULL if the token does not specify
-// a logon SID or in case of an error.
+// Returns the logon SID of a token. Returns nullptr if the token does not
+// specify a logon SID or in case of an error.
 ScopedSid GetLogonSid(HANDLE token);
 
 // Converts a security descriptor in self-relative format to a security
 // descriptor in absolute format.
 bool MakeScopedAbsoluteSd(const ScopedSd& relative_sd,
                           ScopedSd* absolute_sd,
                           ScopedAcl* dacl,
                           ScopedSid* group,
                           ScopedSid* owner,
                           ScopedAcl* sacl);
 
 }  // namespace remoting
 
 #endif  // REMOTING_HOST_WIN_SECURITY_DESCRIPTOR_H_