replace NULL->nullptr in src/remoting.

remoting/protocol/channel_multiplexer_unittest.cc

 // 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.
 
 #include "remoting/protocol/channel_multiplexer.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "net/base/net_errors.h"
@@ skipping 345 matching lines @@
   host_session_.fake_channel_factory().set_fail_create(true);
 
   MockConnectCallback cb1;
   MockConnectCallback cb2;
 
   host_mux_->CreateChannel(kTestChannelName, base::Bind(
       &MockConnectCallback::OnConnected, base::Unretained(&cb1)));
   host_mux_->CreateChannel(kTestChannelName2, base::Bind(
       &MockConnectCallback::OnConnected, base::Unretained(&cb2)));
 
-  EXPECT_CALL(cb1, OnConnectedPtr(NULL))
+  EXPECT_CALL(cb1, OnConnectedPtr(nullptr))
       .Times(AtMost(1))
       .WillOnce(InvokeWithoutArgs(
           this, &ChannelMultiplexerTest::DeleteAfterSessionFail));
   EXPECT_CALL(cb2, OnConnectedPtr(_))
       .Times(0);
 
   base::RunLoop().RunUntilIdle();
 }
 
 }  // namespace protocol
 }  // namespace remoting