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

test/codegen/lib/html/worker_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 worker_test;
+import 'package:unittest/unittest.dart';
+import 'package:unittest/html_individual_config.dart';
+import 'dart:html';
+
+main() {
+  useHtmlIndividualConfiguration();
+
+  group('supported', () {
+    test('supported', () {
+      expect(Worker.supported, isTrue);
+    });
+  });
+
+  var workerScript = '''postMessage('WorkerMessage');''';
+
+  group('functional', () {
+
+    test('unsupported', () {
+      if (!Worker.supported) {
+        expect(() => new Worker('worker.js'), throws);
+      } else {
+        new Worker('worker.js').onError.first.then(expectAsync((e) {
+          // This event is expected, "worker.js" doesn't exist.  But the event
+          // *sometimes* propagates to window.onerror in Firefox which causes
+          // this test to fail, so let's stop any further propagation:
+          e.preventDefault();
+          e.stopImmediatePropagation();
+        }));
+      }
+    });
+
+    if (!Worker.supported) {
+      return;
+    }
+
+    test('works', () {
+      // Use Blob to make a local URL so we don't have to have a separate file.
+      var blob = new Blob([workerScript], 'text/javascript');
+      var url = Url.createObjectUrl(blob);
+      var worker = new Worker(url);
+      var test = expectAsync((e) {
+        expect(e.data, 'WorkerMessage');
+      });
+      worker.onMessage.first.then(test);
+    });
+  });
+}