dart2js: Add elements to the emitter's model.

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

Index: pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart b/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
index 2ae2ef64aea88664c0b6446d387c4e0679bf5224..62a6d45e746e2beb4c16f91b4ca78bd1b658a58d 100644
--- a/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
@@ -301,7 +301,7 @@ class ModelEmitter {
     js.Expression fieldName = js.string(field.name);
     js.Expression code = js.js(getterTemplateFor(field.getterFlags), fieldName);
     String getterName = "${namer.getterPrefix}${field.name}";
-    return new Method(getterName, code);
+    return new StubMethod(getterName, code);
   }
 
   Method _generateSetter(InstanceField field) {
@@ -316,7 +316,7 @@ class ModelEmitter {
     js.Expression fieldName = js.string(field.name);
     js.Expression code = js.js(setterTemplateFor(field.setterFlags), fieldName);
     String setterName = "${namer.setterPrefix}${field.name}";
-    return new Method(setterName, code);
+    return new StubMethod(setterName, code);
   }
 
   Iterable<Method> _generateGettersSetters(Class cls) {