dart2js: Pass type information to constructor rather than add later.

pkg/compiler/lib/src/js_emitter/lazy_emitter/model_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/lazy_emitter/model_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/lazy_emitter/model_emitter.dart b/pkg/compiler/lib/src/js_emitter/lazy_emitter/model_emitter.dart
index 352d7f7885e582bfe6e67342f7bc451c47bbb5e4..b6ecb5b36b05227456fd93d3b14826aec36dde16 100644
--- a/pkg/compiler/lib/src/js_emitter/lazy_emitter/model_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/lazy_emitter/model_emitter.dart
@@ -624,6 +624,9 @@ class ModelEmitter {
     // or RTI. In either case we don't need its fields.
     if (cls.isDirectlyInstantiated && !cls.isNative) {
       fieldNames = cls.fields.map((Field field) => field.name).toList();
+      if (cls.hasRti) {
+        fieldNames.add(namer.rtiFieldName);
+      }
     }
     js.Name name = cls.name;