Use ClassEntity in ClassHierarchyNode

tests/compiler/dart2js/serialization/model_test_helper.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.serialization_model_test;
 
 import 'dart:async';
 import 'dart:io';
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
@@ skipping 300 matching lines @@
 
 void checkClassHierarchyNodes(
     ClosedWorld closedWorld1,
     ClosedWorld closedWorld2,
     ClassHierarchyNode node1,
     ClassHierarchyNode node2,
     {bool verbose: false}) {
   if (verbose) {
     print('Checking $node1 vs $node2');
   }
-  Expect.isTrue(areElementsEquivalent(node1.cls, node2.cls),
-      "Element identity mismatch for ${node1.cls} vs ${node2.cls}.");
+  ClassElement cls1 = node1.cls;
+  ClassElement cls2 = node2.cls;
+  Expect.isTrue(areElementsEquivalent(cls1, cls2),
+      "Element identity mismatch for ${cls1} vs ${cls2}.");
   Expect.equals(
       node1.isDirectlyInstantiated,
       node2.isDirectlyInstantiated,
       "Value mismatch for 'isDirectlyInstantiated' "
-      "for ${node1.cls} vs ${node2.cls}.");
+      "for ${cls1} vs ${cls2}.");
   Expect.equals(
       node1.isIndirectlyInstantiated,
       node2.isIndirectlyInstantiated,
       "Value mismatch for 'isIndirectlyInstantiated' "
       "for ${node1.cls} vs ${node2.cls}.");
   // TODO(johnniwinther): Enforce a canonical and stable order on direct
   // subclasses.
   for (ClassHierarchyNode child in node1.directSubclasses) {
     bool found = false;
     for (ClassHierarchyNode other in node2.directSubclasses) {
-      if (areElementsEquivalent(child.cls, other.cls)) {
+      ClassElement child1 = child.cls;
+      ClassElement child2 = other.cls;
+      if (areElementsEquivalent(child1, child2)) {
         checkClassHierarchyNodes(closedWorld1, closedWorld2, child, other,
             verbose: verbose);
         found = true;
         break;
       }
     }
     if (!found) {
       if (child.isInstantiated) {
         print('Missing subclass ${child.cls} of ${node1.cls} '
             'in ${node2.directSubclasses}');
@@ skipping 101 matching lines @@
 }
 
 bool areInstancesEquivalent(Instance instance1, Instance instance2,
     bool typeEquivalence(ResolutionDartType a, ResolutionDartType b)) {
   ResolutionInterfaceType type1 = instance1.type;
   ResolutionInterfaceType type2 = instance2.type;
   return typeEquivalence(type1, type2) &&
       instance1.kind == instance2.kind &&
       instance1.isRedirection == instance2.isRedirection;
 }