Replace NULL with nullptr or null in webrtc/base/.

webrtc/base/nat_unittest.cc

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 318 matching lines @@
                                     nat_->internal_tcp_address())) {
     int_thread_->Start();
     ext_thread_->Start();
   }
 
   void OnConnectEvent(AsyncSocket* socket) {
     connected_ = true;
   }
 
   void OnAcceptEvent(AsyncSocket* socket) {
-    accepted_.reset(server_->Accept(NULL));
+    accepted_.reset(server_->Accept(nullptr));
   }
 
   void OnCloseEvent(AsyncSocket* socket, int error) {
   }
 
   void ConnectEvents() {
     server_->SignalReadEvent.connect(this, &NatTcpTest::OnAcceptEvent);
     client_->SignalConnectEvent.connect(this, &NatTcpTest::OnConnectEvent);
   }
 
@@ skipping 36 matching lines @@
   size_t len = strlen(buf);
 
   in->Send(buf, len);
   SocketAddress trans_addr;
   EXPECT_TRUE(out->CheckNextPacket(buf, len, &trans_addr));
 
   out->Send(buf, len);
   EXPECT_TRUE(in->CheckNextPacket(buf, len, &trans_addr));
 }
 // #endif