Move unittest from lib to pkg.

tests/json/json_test.dart

 // Copyright (c) 2011, 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('json_tests');
 
 #import('dart:json');
 #import('dart:html');
-#import('../../lib/unittest/unittest.dart');
-#import('../../lib/unittest/html_config.dart');
+#import('../../pkg/unittest/unittest.dart');
+#import('../../pkg/unittest/html_config.dart');
 
 main() {
   useHtmlConfiguration();
   test('Parse', () {
     // Scalars.
     expect(JSON.parse(' 5 '), equals(5));
     expect(JSON.parse(' -42 '), equals(-42));
     expect(JSON.parse(' 3e0 '), equals(3));
     expect(JSON.parse(' 3.14 '), equals(3.14));
     expect(JSON.parse('true '), isTrue);
@@ skipping 112 matching lines @@
 
 /**
  * Checks that the argument can be converted to a JSON string and
  * back, and produce something equivalent to the argument.
  */
 validateRoundTrip(expected) {
   expect(JSON.parse(JSON.stringify(expected)), equals(expected));
 }