replace NULL->nullptr in src/remoting.

remoting/signaling/server_log_entry.cc

Index: remoting/signaling/server_log_entry.cc
diff --git a/remoting/signaling/server_log_entry.cc b/remoting/signaling/server_log_entry.cc
index 684c74e6f8c6014c38fa232b0fa0d8319b663a10..d91a32a970d3d9e8b0164f4dd809faefae9ce7c6 100644
--- a/remoting/signaling/server_log_entry.cc
+++ b/remoting/signaling/server_log_entry.cc
@@ -47,7 +47,7 @@ void ServerLogEntry::AddCpuField() {
 }
 
 void ServerLogEntry::AddModeField(ServerLogEntry::Mode mode) {
-  const char* mode_value = NULL;
+  const char* mode_value = nullptr;
   switch (mode) {
     case IT2ME:
       mode_value = kValueModeIt2Me;