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

test/codegen/lib/html/filereader_test.dart

+// Copyright (c) 2014, 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 filereader_test;
+import 'package:unittest/unittest.dart';
+import 'package:unittest/html_config.dart';
+import 'dart:html';
+import 'dart:typed_data';
+
+main() {
+  useHtmlConfiguration();
+
+  test('readAsText', () {
+      var reader = new FileReader();
+      reader.onLoad.listen(expectAsync((event) {
+        var result = reader.result;
+        expect(result, equals('hello world'));
+      }));
+      reader.readAsText(new Blob(['hello ', 'world']));
+  });
+
+  test('readAsArrayBuffer', () {
+      var reader = new FileReader();
+      reader.onLoad.listen(expectAsync((event) {
+        var result = reader.result;
+        expect(result is Uint8List, isTrue);
+        expect(result, orderedEquals([65, 66, 67]));
+      }));
+      reader.readAsArrayBuffer(new Blob(['ABC']));
+  });
+
+  test('readDataUrl', () {
+      var reader = new FileReader();
+      reader.onLoad.listen(expectAsync((event) {
+        var result = reader.result;
+        expect(result is String, isTrue);
+        expect(result.startsWith('data:'), isTrue);
+      }));
+      reader.readAsDataUrl(new Blob(['ABC']));
+  });
+
+}