Move unittest from lib to pkg.

tests/html/js_interop_4_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('JsInterop4Test');
-#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:isolate');
 
 final testData = const [1, '2', 'true'];
 
 void testIsolateEntry() {
   var fun1 = window.lookupPort('fun1');
   var result = fun1.callSync(testData);
 
   var fun2 = window.lookupPort('fun2');
@@ skipping 37 matching lines @@
       window.setTimeout(done, 0);
     };
 
     var port2 = new ReceivePortSync();
     port2.receive(fun2);
     window.registerPort('fun2', port2.toSendPort());
 
     spawnDomFunction(testIsolateEntry);
   });
 }