Error reporting on File in dart:io

runtime/bin/utils_macos.cc

Index: runtime/bin/utils_macos.cc
diff --git a/runtime/bin/utils_macos.cc b/runtime/bin/utils_macos.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2b7d03b06811be8f7277841e6947a32675da0511
--- /dev/null
+++ b/runtime/bin/utils_macos.cc
@@ -0,0 +1,12 @@
+// 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 <errno.h>
+
+#include "bin/utils.h"
+
+OSError::OSError() {
+  set_code(errno);
+  SetMessage(strerror(errno));
+}