Implement multitest expectations.

pkg/testing/lib/src/test_description.dart

 // Copyright (c) 2016, 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.md file.
 
 library testing.test_description;
 
 import 'dart:io' show
     File,
     FileSystemEntity;
 
 class TestDescription implements Comparable<TestDescription> {
   final Uri root;
   final File file;
   final Uri output;
 
+  /// If non-null, this is a generated multitest, and the set contains the
+  /// expected outcomes.
+  Set<String> multitestExpectations;
+
   TestDescription(this.root, this.file, {this.output});
 
   Uri get uri => file.uri;
 
   String get shortName {
     String baseName = "$uri".substring("$root".length);
     return baseName.substring(0, baseName.length - ".dart".length);
   }
 
   String get escapedName => shortName.replaceAll("/", "__");
@@ skipping 32 matching lines @@
 
   String formatError(String message) {
     String base = Uri.base.toFilePath();
     String path = uri.toFilePath();
     if (path.startsWith(base)) {
       path = path.substring(base.length);
     }
     return "$path:$message";
   }
 }