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

pkg/kernel/lib/transformations/continuation.dart

Index: pkg/kernel/lib/transformations/continuation.dart
diff --git a/pkg/kernel/lib/transformations/continuation.dart b/pkg/kernel/lib/transformations/continuation.dart
index 4e4cdbba40809ca69de429db88538b34cbc7ddfa..5090511ca6230dfd3283dffaef23ce05b0a911e1 100644
--- a/pkg/kernel/lib/transformations/continuation.dart
+++ b/pkg/kernel/lib/transformations/continuation.dart
@@ -20,8 +20,8 @@ void transformLibraries(CoreTypes coreTypes, List<Library> libraries) {
   }
 }
 
-Program transformProgram(Program program) {
-  var helper = new HelperNodes.fromProgram(program);
+Program transformProgram(CoreTypes coreTypes, Program program) {
+  var helper = new HelperNodes.fromCoreTypes(coreTypes);
   var rewriter = new RecursiveContinuationRewriter(helper);
   return rewriter.rewriteProgram(program);
 }
@@ -943,9 +943,4 @@ class HelperNodes {
         coreTypes.awaitHelperProcedure,
         coreTypes);
   }
-
-  factory HelperNodes.fromProgram(Program program) {
-    var coreTypes = new CoreTypes(program);
-    return new HelperNodes.fromCoreTypes(coreTypes);
-  }
 }