Don't recreate CoreTypes in transformers. Pass it in.

pkg/kernel/tool/dartk.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 'dart:async';
 import 'dart:io';
 
 import '../bin/batch_util.dart';
 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/core_types.dart';
 import 'package:kernel/verifier.dart';
 import 'package:kernel/kernel.dart';
 import 'package:kernel/log.dart';
 import 'package:kernel/target/targets.dart';
 import 'package:kernel/transformations/treeshaker.dart';
 import 'package:path/path.dart' as path;
 
 // Returns the path to the current sdk based on `Platform.resolvedExecutable`.
 String currentSdk() {
   // The dart executable should be inside dart-sdk/bin/dart.
@@ skipping 373 matching lines @@
   if (canContinueCompilation) {
     runVerifier();
   }
 
   if (options['link'] && program.mainMethodName == null) {
     fail('[error] The program has no main method.');
   }
 
   // Apply target-specific transformations.
   if (target != null && canContinueCompilation) {
-    target.performModularTransformations(program);
+    CoreTypes coreTypes = new CoreTypes(program);
+    target.performModularTransformations(coreTypes, program);
     runVerifier();
     if (options['link']) {
-      target.performGlobalTransformations(program);
+      target.performGlobalTransformations(coreTypes, program);
       runVerifier();
     }
   }
 
   if (options['no-output']) {
     return CompilerOutcome.Ok;
   }
 
   watch.reset();
 
@@ skipping 23 matching lines @@
     int flushTime = watch.elapsedMilliseconds - time;
     print('writer.flush_time = $flushTime ms');
   }
 
   if (options['tolerant']) {
     return CompilerOutcome.Ok;
   }
 
   return errors.length > 0 ? CompilerOutcome.Fail : CompilerOutcome.Ok;
 }