Extract ClassHierarchyImpl implementation from ClassHierarchy.

pkg/kernel/test/class_hierarchy_self_check.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:test/test.dart';
 import 'class_hierarchy_basic.dart';
 import 'dart:io';
 import 'dart:math';
 import 'self_check_util.dart';
 
 main(List<String> args) {
   runSelfCheck(args, (String filename) {
     testClassHierarchyOnProgram(loadProgramFromBinary(filename));
   });
 }
 
 void testClassHierarchyOnProgram(Program program, {bool verbose: false}) {
   BasicClassHierarchy basic = new BasicClassHierarchy(program);
-  ClassHierarchy classHierarchy = new ClassHierarchy(program);
+  ClassHierarchyImpl classHierarchy = new ClassHierarchyImpl(program);
   int total = classHierarchy.classes.length;
   int progress = 0;
   for (var class1 in classHierarchy.classes) {
     for (var class2 in classHierarchy.classes) {
       bool isSubclass = classHierarchy.isSubclassOf(class1, class2);
       bool isSubmixture = classHierarchy.isSubmixtureOf(class1, class2);
       bool isSubtype = classHierarchy.isSubtypeOf(class1, class2);
       var asInstance = classHierarchy.getClassAsInstanceOf(class1, class2);
       if (isSubclass != basic.isSubclassOf(class1, class2)) {
         fail('isSubclassOf(${class1.name}, ${class2.name}) returned '
@@ skipping 118 matching lines @@
 
 var random = new Random(12345);
 
 List/*<T>*/ pickRandom/*<T>*/(List/*<T>*/ items, int n) {
   var result = /*<T>*/ [];
   for (int i = 0; i < n; ++i) {
     result.add(items[random.nextInt(items.length)]);
   }
   return result;
 }