replace NULL->nullptr in src/remoting.

remoting/host/win/rdp_client.cc

Index: remoting/host/win/rdp_client.cc
diff --git a/remoting/host/win/rdp_client.cc b/remoting/host/win/rdp_client.cc
index 763cfa26b3d72becdee2cb5872791cec129f20f8..f41db108e959dcd658a7282db7783a7dd1781d97 100644
--- a/remoting/host/win/rdp_client.cc
+++ b/remoting/host/win/rdp_client.cc
@@ -166,7 +166,7 @@ void RdpClient::Core::Disconnect() {
 
   // The caller does not expect any notifications to be delivered after this
   // point.
-  event_handler_ = NULL;
+  event_handler_ = nullptr;
 
   // Gracefully shutdown the RDP connection.
   if (rdp_client_window_) {
@@ -200,7 +200,7 @@ void RdpClient::Core::OnDisconnected() {
 
   // Delay window destruction until no ActiveX control's code is on the stack.
   ui_task_runner_->DeleteSoon(FROM_HERE, rdp_client_window_.release());
-  self_ = NULL;
+  self_ = nullptr;
 }
 
 RdpClient::Core::~Core() {
@@ -228,7 +228,7 @@ void RdpClient::Core::NotifyClosed() {
 
   if (event_handler_) {
     RdpClient::EventHandler* event_handler = event_handler_;
-    event_handler_ = NULL;
+    event_handler_ = nullptr;
     event_handler->OnRdpClosed();
   }
 }