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

pkg/front_end/lib/src/fasta/fasta.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 fasta;
 
 import 'dart:async' show Future;
 
 import 'dart:convert' show JSON;
 
 import 'dart:io' show BytesBuilder, Directory, File, exitCode;
 
 import 'package:front_end/file_system.dart';
 import 'package:front_end/physical_file_system.dart';
 import 'package:front_end/src/fasta/kernel/utils.dart';
 import 'package:kernel/binary/ast_to_binary.dart'
     show LibraryFilteringBinaryPrinter;
 
+import 'package:kernel/core_types.dart' show CoreTypes;
+
 import 'package:kernel/kernel.dart' show Library, Program, loadProgramFromBytes;
 
 import 'package:kernel/target/targets.dart' show Target, TargetFlags, getTarget;
 
 import 'compiler_command_line.dart' show CompilerCommandLine;
 
 import 'compiler_context.dart' show CompilerContext;
 
 import 'errors.dart' show InputError, formatUnexpected, inputError, reportCrash;
 
@@ skipping 184 matching lines @@
     } on InputError catch (e) {
       return new CompilationResult.error(e.format());
     }
 
     if (program.mainMethod == null) {
       return new CompilationResult.error("No 'main' method found.");
     }
 
     // Perform target-specific transformations.
     Target target = getTarget("vm", new TargetFlags(strongMode: false));
-    target.performModularTransformations(program);
-    target.performGlobalTransformations(program);
+    CoreTypes coreTypes = new CoreTypes(program);
+    target.performModularTransformations(coreTypes, program);
+    target.performGlobalTransformations(coreTypes, program);
 
     // Write the program to a list of bytes and return it.  Do not include
     // libraries that have a dart: import URI.
     //
     // TODO(kmillikin): This is intended to exclude platform libraries that are
     // included in the Kernel binary platform platform.dill.  It does not
     // necessarily exclude exactly the platform libraries.  Use a better
     // predicate that knows what is included in platform.dill.
     var sink = new ByteSink();
     bool predicate(Library library) => !library.importUri.isScheme('dart');
@@ skipping 66 matching lines @@
   final BytesBuilder builder = new BytesBuilder();
 
   void add(List<int> data) {
     builder.add(data);
   }
 
   void close() {
     // Nothing to do.
   }
 }