Pass ClassHierarchy instead of creating it.

pkg/kernel/tool/dartk.dart

Index: pkg/kernel/tool/dartk.dart
diff --git a/pkg/kernel/tool/dartk.dart b/pkg/kernel/tool/dartk.dart
index 35d97243d714d6f362e8f07b2f51ef4607111d8a..e42e9f33db638d7a14bf33ff2e145a9bea6c92f3 100755
--- a/pkg/kernel/tool/dartk.dart
+++ b/pkg/kernel/tool/dartk.dart
@@ -12,6 +12,7 @@ import '../bin/util.dart';
 import 'package:args/args.dart';
 import 'package:analyzer/src/kernel/loader.dart';
 import 'package:kernel/application_root.dart';
+import 'package:kernel/class_hierarchy.dart';
 import 'package:kernel/core_types.dart';
 import 'package:kernel/verifier.dart';
 import 'package:kernel/kernel.dart';
@@ -407,7 +408,8 @@ Future<CompilerOutcome> batchMain(
   // Apply target-specific transformations.
   if (target != null && canContinueCompilation) {
     CoreTypes coreTypes = new CoreTypes(program);
-    target.performModularTransformations(coreTypes, program);
+    ClassHierarchy hierarchy = new ClosedWorldClassHierarchy(program);
+    target.performModularTransformations(coreTypes, hierarchy, program);
     runVerifier();
     if (options['link']) {
       target.performGlobalTransformations(coreTypes, program);