Fix the definition of kIllegalPort in dart_api.h.

samples/sample_extension/sample_extension.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 #include <string.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include "dart_api.h"
 
 Dart_NativeFunction ResolveName(Dart_Handle name, int argc);
 
@@ skipping 78 matching lines @@
   Dart_CObject result;
   result.type = Dart_CObject::kNull;
   Dart_PostCObject(reply_port_id, &result);
 }
 
 void randomArrayServicePort(Dart_NativeArguments arguments) {
   Dart_EnterScope();
   Dart_SetReturnValue(arguments, Dart_Null());
   Dart_Port service_port =
       Dart_NewNativePort("RandomArrayService", wrappedRandomArray, true);
-  if (service_port != kIllegalPort) {
+  if (service_port != ILLEGAL_PORT) {
     Dart_Handle send_port = HandleError(Dart_NewSendPort(service_port));
     Dart_SetReturnValue(arguments, send_port);
   }
   Dart_ExitScope();
 }
 
 
 struct FunctionLookup {
   const char* name;
   Dart_NativeFunction function;
@@ skipping 14 matching lines @@
 
   for (int i=0; function_list[i].name != NULL; ++i) {
     if (strcmp(function_list[i].name, cname) == 0) {
       result = function_list[i].function;
       break;
     }
   }
   Dart_ExitScope();
   return result;
 }