Add all dart:html tests from the sdk to test/codegen.

test/codegen/lib/html/resource_http_test.dart

+// Copyright (c) 2015, 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 resource_http_test;
+import 'dart:async';
+import 'package:unittest/html_individual_config.dart';
+import 'package:unittest/unittest.dart';
+
+main() {
+  useHtmlIndividualConfiguration();
+  // Cache blocker is a workaround for:
+  // https://code.google.com/p/dart/issues/detail?id=11834
+  var cacheBlocker = new DateTime.now().millisecondsSinceEpoch;
+  var url = '/root_dart/tests/html/resource_data.txt?cacheBlock=$cacheBlocker';
+
+  void validateResponse(data) {
+    expect(data, equals('This file was read by a Resource!'));
+  }
+
+  group('resource', () {
+    test('readAsString', () async {
+      Resource r = new Resource(url);
+      var data = await r.readAsString();
+      validateResponse(data);
+    });
+    test('readAsBytes', () async {
+      Resource r = new Resource(url);
+      var data = await r.readAsBytes();
+      validateResponse(new String.fromCharCodes(data));
+    });
+    test('openRead', () async {
+      Resource r = new Resource(url);
+      var bytes = [];
+      await for (var b in r.openRead()) {
+        bytes.addAll(b);
+      }
+      validateResponse(new String.fromCharCodes(bytes));
+    });
+  });
+}