Error reporting on File in dart:io

runtime/bin/directory.dart

Index: runtime/bin/directory.dart
diff --git a/runtime/bin/directory.dart b/runtime/bin/directory.dart
index dd6bf149d09667dd7117d7b1fec2f7e547a691a6..845bb9b8a43c6c632d858fc1448d5287390ce16f 100644
--- a/runtime/bin/directory.dart
+++ b/runtime/bin/directory.dart
@@ -145,8 +145,14 @@ interface Directory default _Directory {
 
 
 class DirectoryException {
-  const DirectoryException([String this.message, int this.errorCode = 0]);
-  String toString() => "DirectoryException: $message";
+  const DirectoryException(String this.message, [this.osError = null]);
+  String toString() {
+    String result = "DirectoryException: $message";
+    if (osError != null) {
+      result = "$result (${osError.toString()})";
+    }
+    return result;
+  }
   final String message;
-  final int errorCode;
+  final OSError osError;
 }