Extract ClassHierarchyImpl implementation from ClassHierarchy.

pkg/kernel/test/class_hierarchy_bench.dart

 #!/usr/bin/env 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 file.
 import 'package:kernel/kernel.dart';
 import 'package:kernel/class_hierarchy.dart';
 import 'package:args/args.dart';
 import 'class_hierarchy_basic.dart';
 import 'dart:math';
 import 'dart:io';
@@ skipping 37 matching lines @@
   buildHierarchy();
   int coldBuildTime = watch.elapsedMilliseconds;
   watch.reset();
   const int numBuildTrials = 100;
   for (int i = 0; i < numBuildTrials; i++) {
     buildHierarchy();
   }
   int hotBuildTime = watch.elapsedMilliseconds ~/ numBuildTrials;
 
   int hierarchyCount = int.parse(options['cycle']);
-  var hierarchies = <ClassHierarchy>[];
+  var hierarchies = <ClosedWorldClassHierarchy>[];
   for (int i = 0; i < hierarchyCount; i++) {
     hierarchies.add(buildHierarchy());
   }
 
   int currentHierarchy = 0;
-  ClassHierarchy getClassHierarchy() {
+  ClosedWorldClassHierarchy getClassHierarchy() {
     currentHierarchy = (currentHierarchy + 1) % hierarchies.length;
     return hierarchies[currentHierarchy];
   }
 
   Random rnd = new Random(12345);
   const int numQueryTrials = 100000;
 
   // Measure isSubclassOf, isSubmixtureOf, isSubtypeOf, getClassAsInstanceOf.
 
   // Warm-up run to ensure the JIT compiler does not favor the first query we
@@ skipping 261 matching lines @@
       : list[mid].toDouble();
 }
 
 num sum(Iterable<num> values) {
   num result = 0;
   for (var x in values) {
     result += x;
   }
   return result;
 }