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

test/codegen/lib/html/css_rule_list_test.dart

+library CssRuleListTest;
+import 'package:unittest/unittest.dart';
+import 'package:unittest/html_config.dart';
+import 'dart:html';
+
+main() {
+
+  var isCssRuleList =
+      predicate((x) => x is List<CssRule>, 'is a List<CssRule>');
+
+  useHtmlConfiguration();
+
+  test("ClientRectList test", () {
+    var sheet = document.styleSheets[0];
+    List<CssRule> rulesList = sheet.cssRules;
+    expect(rulesList, isCssRuleList);
+  });
+}