Add support for getting OS error information for creating temporary directories

runtime/bin/directory.dart

Index: runtime/bin/directory.dart
diff --git a/runtime/bin/directory.dart b/runtime/bin/directory.dart
index 222b3de471b3ebd5ca60ca1ca5cc8b2a5e115a78..acdcd09444312e0f95e231102ee08d697700ee9c 100644
--- a/runtime/bin/directory.dart
+++ b/runtime/bin/directory.dart
@@ -101,7 +101,8 @@ interface Directory factory _Directory {
 
 
 class DirectoryException {
-  const DirectoryException(String this.message);
+  const DirectoryException([String this.message, int this.errorCode = 0]);
   String toString() => "DirectoryException: $message";
   final String message;
+  final int errorCode;
 }