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

test/codegen/lib/html/storage_test.dart

+library StorageTest;
+import 'package:unittest/unittest.dart';
+import 'package:unittest/html_config.dart';
+import 'dart:html';
+
+main() {
+  useHtmlConfiguration();
+  test('GetItem', () {
+    final value = window.localStorage['does not exist'];
+    expect(value, isNull);
+  });
+  test('SetItem', () {
+    final key = 'foo';
+    final value = 'bar';
+    window.localStorage[key] = value;
+    final stored = window.localStorage[key];
+    expect(stored, value);
+  });
+
+  test('event', () {
+    // Bug 8076 that not all optional params are optional in Dartium.
+    var event = new StorageEvent('something', oldValue: 'old', newValue: 'new',
+        url: 'url', key: 'key');
+    expect(event is StorageEvent, isTrue);
+    expect(event.oldValue, 'old');
+    expect(event.newValue, 'new');
+  });
+}