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

pkg/kernel/lib/target/targets.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.target.targets;
 
 import '../ast.dart';
 import '../core_types.dart';
 import '../transformations/treeshaker.dart' show ProgramRoot;
 import 'flutter.dart';
 import 'vm.dart';
@@ skipping 53 matching lines @@
 
   bool get strongMode;
 
   /// If true, the SDK should be loaded in strong mode.
   bool get strongModeSdk => strongMode;
 
   /// Perform target-specific modular transformations.
   ///
   /// These transformations should not be whole-program transformations.  They
   /// should expect that the program will contain external libraries.
-  void performModularTransformations(Program program);
+  void performModularTransformations(CoreTypes coreTypes, Program program);
 
   /// Perform target-specific whole-program transformations.
   ///
   /// These transformations should be optimizations and not required for
   /// correctness.  Everything should work if a simple and fast linker chooses
   /// not to apply these transformations.
-  void performGlobalTransformations(Program program);
+  void performGlobalTransformations(CoreTypes coreTypes, Program program);
 
   /// Builds an expression that instantiates an [Invocation] that can be passed
   /// to [noSuchMethod].
   Expression instantiateInvocation(Member target, Expression receiver,
       String name, Arguments arguments, int offset, bool isSuper);
 
   String toString() => 'Target($name)';
 }
 
 class NoneTarget extends Target {
   final TargetFlags flags;
 
   NoneTarget(this.flags);
 
   bool get strongMode => flags.strongMode;
   String get name => 'none';
   List<String> get extraRequiredLibraries => <String>[];
-  void performModularTransformations(Program program) {}
-  void performGlobalTransformations(Program program) {}
+  void performModularTransformations(CoreTypes coreTypes, Program program) {}
+  void performGlobalTransformations(CoreTypes coreTypes, Program program) {}
 
   @override
   Expression instantiateInvocation(Member target, Expression receiver,
       String name, Arguments arguments, int offset, bool isSuper) {
     return new InvalidExpression();
   }
 }