Support compiling templates in the browser.

test/testing.dart

 // Copyright (c) 2012, 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.
 
 /** Common definitions used for setting up the test environment. */
 library testing;
 
 import 'package:html5lib/dom.dart';
-import 'package:html5lib/html5parser.dart';
+import 'package:html5lib/parser.dart';
 import 'package:web_components/src/template/world.dart';
 
 // TODO(jmesserly): we need tests for warnings from the analyzer.
 class MockWorld extends World {
   MockWorld() : super(null);
   warning(message, [span, span1, span2]) {}
   error(message, [span, span1, span2]) {}
 }
 
 useMockWorld() {
   // TODO(jmesserly): fix the warning system to not need this.
   world = new MockWorld();
 }
 
 Element parseSubtree(String html) => parseFragment(html).nodes[0];