Fix type mismatch in directory listing.

runtime/bin/directory_impl.dart

Index: runtime/bin/directory_impl.dart
diff --git a/runtime/bin/directory_impl.dart b/runtime/bin/directory_impl.dart
index cf90e667037506da9352c6d4f7e322875c30c514..489242c367aafae0eeb09adc76ee1f1cbe590d2a 100644
--- a/runtime/bin/directory_impl.dart
+++ b/runtime/bin/directory_impl.dart
@@ -28,10 +28,10 @@ class _DirectoryListingIsolate extends Isolate {
   void _list(String dir,
              int id,
              bool recursive,
-             ReceivePort dirHandler,
-             ReceivePort fileHandler,
-             ReceivePort doneHandler,
-             ReceivePort dirErrorHandler) native "Directory_List";
+             SendPort dirHandler,
+             SendPort fileHandler,
+             SendPort doneHandler,
+             SendPort dirErrorHandler) native "Directory_List";
 }