Print out experimental test.py reproduction command

tools/testing/dart/utils.dart

 // Copyright (c) 2013, 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.
 
 library utils;
 
 import 'dart:io';
 import 'dart:async';
 import 'dart:utf' as utf;
 
@@ skipping 57 matching lines @@
   return utf.encodeUtf8(string);
 }
 
 // TODO(kustermann,ricow): As soon we have a debug log we should log
 // invalid utf8-encoded input to the log.
 // Currently invalid bytes will be replaced by a replacement character.
 String decodeUtf8(List<int> bytes) {
   return utf.decodeUtf8(bytes);
 }
 
+// This function is pretty stupid and only puts quotes around an argument if
+// it the argument contains a space.
+String escapeCommandLineArgument(String argument) {
+  if (argument.contains(' ')) {
+    return '"$argument"';
+  }
+  return argument;
+}
+