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

pkg/kernel/lib/transformations/generic_types_reification.dart

Index: pkg/kernel/lib/transformations/generic_types_reification.dart
diff --git a/pkg/kernel/lib/transformations/generic_types_reification.dart b/pkg/kernel/lib/transformations/generic_types_reification.dart
index ea645170be317d00864960cd219cf58cb536e3d6..8bdf691cd62a1eda872242b2e6b3506c38f065e5 100644
--- a/pkg/kernel/lib/transformations/generic_types_reification.dart
+++ b/pkg/kernel/lib/transformations/generic_types_reification.dart
@@ -5,10 +5,10 @@
 library kernel.transformation.generic_types_reification;
 
 import '../ast.dart' show Program;
-
+import '../core_types.dart' show CoreTypes;
 import '../transformations/reify/reify_transformer.dart' as reify
     show transformProgram;
 
-Program transformProgram(Program program) {
-  return reify.transformProgram(program);
+Program transformProgram(CoreTypes coreTypes, Program program) {
+  return reify.transformProgram(coreTypes, program);
 }