Test closed world model after deserialization.

pkg/compiler/lib/src/universe/class_set.dart

 // Copyright (c) 2015, 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 dart2js.world.class_set;
 
 import 'dart:collection' show
     IterableBase;
 import '../elements/elements.dart' show
     ClassElement;
@@ skipping 163 matching lines @@
     }
   }
 
   /// Adds [subclass] as a direct subclass of [cls].
   void addDirectSubclass(ClassHierarchyNode subclass) {
     assert(subclass.cls.superclass == cls);
     assert(!_directSubclasses.contains(subclass));
     _directSubclasses = _directSubclasses.prepend(subclass);
   }
 
+  Iterable<ClassHierarchyNode> get directSubclasses => _directSubclasses;
+
   /// Returns `true` if [other] is contained in the subtree of this node.
   ///
   /// This means that [other] is a subclass of [cls].
   bool contains(ClassElement other) {
     while (other != null) {
       if (cls == other) return true;
       if (cls.hierarchyDepth >= other.hierarchyDepth) return false;
       other = other.superclass;
     }
     return false;
@@ skipping 683 matching lines @@
   /// Iteration stops immediately.
   STOP,
   /// Iteration skips the subclasses of the current class.
   SKIP_SUBCLASSES,
 }
 
 /// Visiting function used for the `forEachX` functions of [ClassHierarchyNode]
 /// and [ClassSet]. The return value controls the continued iteration. If `null`
 /// is returned, iteration continues to the end.
 typedef IterationStep ForEachFunction(ClassElement cls);