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

pkg/kernel/lib/transformations/closure_conversion.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.
 
 library kernel.transformations.closure_conversion;
 
 import '../ast.dart' show Class, Program;
 
 import '../core_types.dart' show CoreTypes;
 
 import 'closure/converter.dart' show ClosureConverter;
 
 import 'closure/info.dart' show ClosureInfo;
 
 import 'closure/invalidate_closures.dart';
 import 'closure/mock.dart' show mockUpContext;
 
-Program transformProgram(Program program) {
+Program transformProgram(CoreTypes coreTypes, Program program) {
   var info = new ClosureInfo();
   info.visitProgram(program);
 
-  CoreTypes coreTypes = new CoreTypes(program);
   Class contextClass = mockUpContext(coreTypes, program);
   var convert = new ClosureConverter(coreTypes, info, contextClass);
   program = convert.visitProgram(program);
   return new InvalidateClosures().visitProgram(program);
 }