replace NULL->nullptr in src/remoting.

remoting/host/it2me/it2me_native_messaging_host_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/it2me/it2me_native_messaging_host.h"
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
@@ skipping 444 matching lines @@
 
 void It2MeNativeMessagingHostTest::StopHost() {
   DCHECK(host_task_runner_->RunsTasksOnCurrentThread());
 
   pipe_.reset();
 
   // Wait till all shutdown tasks have completed.
   base::RunLoop().RunUntilIdle();
 
   // Trigger a test shutdown via ExitTest().
-  host_task_runner_ = NULL;
+  host_task_runner_ = nullptr;
 }
 
 void It2MeNativeMessagingHostTest::ExitTest() {
   if (!test_message_loop_->message_loop_proxy()->RunsTasksOnCurrentThread()) {
     test_message_loop_->message_loop_proxy()->PostTask(
         FROM_HERE,
         base::Bind(&It2MeNativeMessagingHostTest::ExitTest,
                    base::Unretained(this)));
     return;
   }
@@ skipping 77 matching lines @@
 
 // Verify rejection if type is unrecognized.
 TEST_F(It2MeNativeMessagingHostTest, InvalidType) {
   base::DictionaryValue message;
   message.SetString("type", "xxx");
   TestBadRequest(message, true);
 }
 
 }  // namespace remoting