replace NULL->nullptr in src/remoting.

remoting/host/token_validator_base.cc

Index: remoting/host/token_validator_base.cc
diff --git a/remoting/host/token_validator_base.cc b/remoting/host/token_validator_base.cc
index 15f22bc1093540015ae01688125fc250e7b785ab..5e3d75db585f1ef0baa093766f1996e3ecd570e8 100644
--- a/remoting/host/token_validator_base.cc
+++ b/remoting/host/token_validator_base.cc
@@ -122,7 +122,7 @@ void TokenValidatorBase::OnCertificateRequested(
   client_cert_store = new net::ClientCertStoreMac();
 #elif defined(USE_OPENSSL)
     // OpenSSL does not use the ClientCertStore infrastructure.
-  client_cert_store = NULL;
+  client_cert_store = nullptr;
 #else
 #error Unknown platform.
 #endif
@@ -150,7 +150,7 @@ void TokenValidatorBase::OnCertificatesSelected(
         return;
       }
     }
-    request_->ContinueWithCertificate(NULL);
+    request_->ContinueWithCertificate(nullptr);
   }
 }