Initial tests for JS interop

tests/html/js_interop_1_test.dart

+// Copyright (c) 2012, 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('JsInterop1Test');
+#import('../../lib/unittest/unittest.dart');
+#import('../../lib/unittest/html_config.dart');
+#import('dart:html');
+#import('dart:json');
+
+injectSource(code) {
+  final script = new ScriptElement();
+  script.type = 'text/javascript';
+  script.innerHTML = code;
+  document.body.nodes.add(script);
+}
+
+main() {
+  useHtmlConfiguration();
+  var callback;
+
+  test('jsPostMessage', () {
+    callback = expectAsync1((e) {
+      Expect.equals('hello', e.data);
+      window.on.message.remove(callback);
+    });
+    window.on.message.add(callback);
+    injectSource("window.postMessage('hello', '*');");
+  });
+}