Start cleaning up the HTML tests.

pkg/dev_compiler/test/codegen/lib/html/custom_tags_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.
 
-library custom_tags_test;
-import 'package:unittest/unittest.dart';
-import 'package:unittest/html_config.dart';
 import 'dart:html';
+
+import 'package:minitest/minitest.dart';
+
 import 'utils.dart';
 
 main() {
-  useHtmlConfiguration();
-
   test('create via custom tag', () {
     var element = new Element.tag('x-basic1')..id = 'basic1';
     document.body.nodes.add(element);
 
     var queryById = query('#basic1');
     expect(queryById, equals(element));
 
     var queryByTag = queryAll('x-basic1');
     expect(queryByTag.length, equals(1));
     expect(queryByTag[0], equals(element));
@@ skipping 16 matching lines @@
   test('type extension inner html', () {
     var element = new DivElement();
     element.setInnerHtml("<div is='x-basic3' id='basic3'></div>",
         treeSanitizer: new NullTreeSanitizer());
     document.body.nodes.add(element);
 
     var queryById = query('#basic3');
     expect(queryById is DivElement, isTrue);
   });
 }