Bring back initPolymer, allow boot.js only if using "polymer_experimental.html".

pkg/polymer/test/noscript_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:template_binding/template_binding.dart';
 
 Future<List<MutationRecord>> onMutation(Node node) {
   var completer = new Completer();
   new MutationObserver((mutations, observer) {
     observer.disconnect();
     completer.complete(mutations);
   })..observe(node, childList: true, subtree: true);
   return completer.future;
 }
 
-@initMethod
-main() {
+main() => initPolymer().run(() {
   useHtmlConfiguration();
 
   var ready = Polymer.onReady.then((_) {
     var a = querySelector("#a");
     templateBind(a).model = "foo";
     return onMutation(a.parent);
   });
 
   setUp(() => ready);
 
   test('template found with multiple noscript declarations', () {
     expect(querySelector('x-a').shadowRoot.nodes.first.text, 'a');
     expect(querySelector('x-c').shadowRoot.nodes.first.text, 'c');
     expect(querySelector('x-b').shadowRoot.nodes.first.text, 'b');
     expect(querySelector('x-d').shadowRoot.nodes.first.text, 'd');
   });
-}
+});