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

pkg/kernel/test/treeshaker_membench.dart

Index: pkg/kernel/test/treeshaker_membench.dart
diff --git a/pkg/kernel/test/treeshaker_membench.dart b/pkg/kernel/test/treeshaker_membench.dart
index 275fd182834bab6d185c841be2372f344f580fab..8147445034d8af79e378e4eff95ea53c5adf17a6 100644
--- a/pkg/kernel/test/treeshaker_membench.dart
+++ b/pkg/kernel/test/treeshaker_membench.dart
@@ -45,8 +45,8 @@ main(List<String> args) {
   int copyCount = int.parse(options['count']);
 
   TreeShaker buildTreeShaker() {
-    return new TreeShaker(program,
-        hierarchy: hierarchy, coreTypes: coreTypes, strongMode: strongMode);
+    return new TreeShaker(coreTypes, program,
+        hierarchy: hierarchy, strongMode: strongMode);
   }
 
   List<TreeShaker> keepAlive = <TreeShaker>[];