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

webrtc/base/asyncpacketsocket.h

 /*
  *  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 60 matching lines @@
     STATE_CLOSED,
     STATE_BINDING,
     STATE_BOUND,
     STATE_CONNECTING,
     STATE_CONNECTED
   };
 
   AsyncPacketSocket();
   ~AsyncPacketSocket() override;
 
-  // Returns current local address. Address may be set to NULL if the
+  // Returns current local address. Address may be set to null if the
   // socket is not bound yet (GetState() returns STATE_BINDING).
   virtual SocketAddress GetLocalAddress() const = 0;
 
   // Returns remote address. Returns zeroes if this is not a client TCP socket.
   virtual SocketAddress GetRemoteAddress() const = 0;
 
   // Send a packet.
   virtual int Send(const void *pv, size_t cb, const PacketOptions& options) = 0;
   virtual int SendTo(const void *pv, size_t cb, const SocketAddress& addr,
                      const PacketOptions& options) = 0;
@@ skipping 42 matching lines @@
   // Used only for listening TCP sockets.
   sigslot::signal2<AsyncPacketSocket*, AsyncPacketSocket*> SignalNewConnection;
 
  private:
   RTC_DISALLOW_COPY_AND_ASSIGN(AsyncPacketSocket);
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_ASYNCPACKETSOCKET_H_