replace NULL->nullptr in src/remoting.

remoting/host/native_messaging/native_messaging_writer_unittest.cc

Index: remoting/host/native_messaging/native_messaging_writer_unittest.cc
diff --git a/remoting/host/native_messaging/native_messaging_writer_unittest.cc b/remoting/host/native_messaging/native_messaging_writer_unittest.cc
index 38817fd6e5e3dfd7e774c6b65792211afa0a0e58..fddd7e7a08053fc31c234be24684bf902dbc0fc3 100644
--- a/remoting/host/native_messaging/native_messaging_writer_unittest.cc
+++ b/remoting/host/native_messaging/native_messaging_writer_unittest.cc
@@ -55,7 +55,7 @@ TEST_F(NativeMessagingWriterTest, GoodMessage) {
 
   // Nothing more should have been written. Close the write-end of the pipe,
   // and verify the read end immediately hits EOF.
-  writer_.reset(NULL);
+  writer_.reset(nullptr);
   char unused;
   read = read_file_.ReadAtCurrentPos(&unused, 1);
   EXPECT_LE(read, 0);
@@ -67,7 +67,7 @@ TEST_F(NativeMessagingWriterTest, SecondMessage) {
   message2.SetInteger("foo", 42);
   EXPECT_TRUE(writer_->WriteMessage(message1));
   EXPECT_TRUE(writer_->WriteMessage(message2));
-  writer_.reset(NULL);
+  writer_.reset(nullptr);
 
   // Read two messages.
   uint32 length;