Fix the definition of kIllegalPort in dart_api.h.

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index ed25d6e05ff940db8c8e8e1510f478adc07c0202..eebf7632abbe667a9562e07260401e8347187e5c 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -953,7 +953,6 @@ DART_EXPORT void Dart_InterruptIsolate(Dart_Isolate isolate) {
 
 // --- Messages and Ports ---
 
-
 DART_EXPORT void Dart_SetMessageNotifyCallback(
     Dart_MessageNotifyCallback message_notify_callback) {
   Isolate* isolate = Isolate::Current();
@@ -1082,7 +1081,7 @@ DART_EXPORT Dart_Port Dart_NewNativePort(const char* name,
   if (handler == NULL) {
     OS::PrintErr("%s expects argument 'handler' to be non-null.\n",
                  CURRENT_FUNC);
-    return kIllegalPort;
+    return ILLEGAL_PORT;
   }
   // Start the native port without a current isolate.
   IsolateSaver saver(Isolate::Current());