Enables codegen support in polymer

pkg/polymer/test/prop_attr_reflection_test.dart

Index: pkg/polymer/test/prop_attr_reflection_test.dart
diff --git a/pkg/polymer/test/prop_attr_reflection_test.dart b/pkg/polymer/test/prop_attr_reflection_test.dart
index 79b9c8eb55be72baf4442909d72842bdea7108d5..657a876246131ad2e6e698a67bf623e3321e3239 100644
--- a/pkg/polymer/test/prop_attr_reflection_test.dart
+++ b/pkg/polymer/test/prop_attr_reflection_test.dart
@@ -7,6 +7,7 @@ import 'dart:html';
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 import 'package:polymer/polymer.dart';
+import 'package:smoke/mirrors.dart';
 
 class XFoo extends PolymerElement {
   XFoo.created() : super.created();
@@ -41,6 +42,10 @@ Future onAttributeChange(Element node) {
 }
 
 main() {
+  // The static configuration is not complete because of the missing @CustomTag.
+  // TODO(sigmund): add a different annotation for this? (dartbug.com/17790)
+  useMirrors();
+
   initPolymer();
   useHtmlConfiguration();