Move unittest from lib to pkg.

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('../../pkg/unittest/unittest.dart');
+#import('../../pkg/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('js-to-dart-post-message', () {
     callback = expectAsync1((e) {
       Expect.equals('hello', e.data);
       window.on.message.remove(callback);
     });
     window.on.message.add(callback);
     injectSource("window.postMessage('hello', '*');");
   });
 }