replace NULL->nullptr in src/remoting.

remoting/host/pairing_registry_delegate_win_unittest.cc

 // Copyright 2013 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/pairing_registry_delegate_win.h"
 
 #include <shlwapi.h>
 
 #include "base/guid.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 94 matching lines @@
       new PairingRegistryDelegateWin());
   delegate->SetRootKeys(privileged_.Handle(), unprivileged_.Handle());
 
   PairingRegistry::Pairing pairing(base::Time::Now(), "xxx", "xxx", "xxx");
   EXPECT_TRUE(delegate->Save(pairing));
   EXPECT_EQ(delegate->Load(pairing.client_id()), pairing);
 
   // Strip the delegate from write access and validate that it still can be used
   // to read the pairings.
   delegate.reset(new PairingRegistryDelegateWin());
-  delegate->SetRootKeys(NULL, unprivileged_.Handle());
+  delegate->SetRootKeys(nullptr, unprivileged_.Handle());
 
   PairingRegistry::Pairing unprivileged_pairing =
       delegate->Load(pairing.client_id());
   EXPECT_EQ(pairing.client_id(), unprivileged_pairing.client_id());
   EXPECT_EQ(pairing.client_name(), unprivileged_pairing.client_name());
   EXPECT_EQ(pairing.created_time(), unprivileged_pairing.created_time());
 
   // Verify that the shared secret if not available.
   EXPECT_TRUE(unprivileged_pairing.shared_secret().empty());
 
   // Verify that a pairing cannot be saved.
   EXPECT_FALSE(delegate->Save(pairing));
 }
 
 }  // namespace remoting