Enables codegen support in polymer

pkg/polymer/test/prop_attr_reflection_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
 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();
 
   @observable var foo = '';
   @observable String baz = '';
 }
 
 class XBar extends XFoo {
   XBar.created() : super.created();
@@ skipping 14 matching lines @@
   var completer = new Completer();
   new MutationObserver((records, observer) {
     observer.disconnect();
     completer.complete();
   })..observe(node, attributes: true);
   scheduleMicrotask(Observable.dirtyCheck);
   return completer.future;
 }
 
 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();
 
   setUp(() => Polymer.onReady);
 
   // Most tests use @CustomTag, here we test out the impertive register:
   Polymer.register('x-foo', XFoo);
   Polymer.register('x-bar', XBar);
   Polymer.register('x-compose', XCompose);
 
@@ skipping 56 matching lines @@
       expect(xbar.attributes.containsKey('zim'), false, reason:
           'attribute reflects false valued boolean property as NOT '
           'having attribute');
       xbar.obj = 'hi';
     }).then((_) => onAttributeChange(xbar)).then((_) {
       expect(xbar.attributes['obj'], 'hi', reason:
           'reflect property based on current type');
     });
   });
 }