Fixes memory leak of async directory lister

runtime/bin/directory_unsupported.cc

Index: runtime/bin/directory_unsupported.cc
diff --git a/runtime/bin/directory_unsupported.cc b/runtime/bin/directory_unsupported.cc
index 7e82bdd81fd70f7c64b57697f35e108d22e7a291..1b1abd27c29cc958cdf23307419358a60bc56a86 100644
--- a/runtime/bin/directory_unsupported.cc
+++ b/runtime/bin/directory_unsupported.cc
@@ -64,6 +64,20 @@ void FUNCTION_NAME(Directory_List)(Dart_NativeArguments args) {
         "Directory is not supported on this platform"));
 }
 
+
+void FUNCTION_NAME(Directory_GetAsyncDirectoryListerPointer)(
+    Dart_NativeArguments args) {
+  Dart_ThrowException(DartUtils::NewInternalError(
+        "Directory is not supported on this platform"));
+}
+
+
+void FUNCTION_NAME(Directory_SetAsyncDirectoryListerPointer)(
+    Dart_NativeArguments args) {
+  Dart_ThrowException(DartUtils::NewInternalError(
+        "Directory is not supported on this platform"));
+}
+
 }  // namespace bin
 }  // namespace dart