Use expect instead of unittest for json_lib_test.

pkg/dev_compiler/test/browser/language_tests.js

 // Copyright (c) 2015, 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.
 
 define(['dart_sdk', 'async_helper', 'unittest', 'require'],
       function(dart_sdk, async_helper, unittest, require) {
   'use strict';
 
   async_helper = async_helper.async_helper;
 
@@ skipping 373 matching lines @@
       'default_arguments_test': fail
     },
 
     'lib/convert': {
       'encoding_test': skip_timeout,
 
       // TODO(jmesserly): this is in an inconsistent state between our old and
       // newer SDKs.
       'html_escape_test': ['skip'],
 
-      'json_lib_test': 'unittest',
-
       'json_utf8_chunk_test': skip_timeout,
       'latin1_test': skip_timeout,
 
       'streamed_conversion_json_encode1_test': skip_timeout,
       'streamed_conversion_json_utf8_decode_test': skip_timeout,
       'streamed_conversion_json_utf8_encode_test': skip_timeout,
       'streamed_conversion_utf8_decode_test': skip_timeout,
       'streamed_conversion_utf8_encode_test': skip_timeout,
       'utf85_test': skip_timeout,
     },
@@ skipping 488 matching lines @@
 
     for (let action of unittest_tests) {
       try {
         action();
       } catch (e) {
         console.error("Caught error tying to setup test:", e);
       }
     }
   });
 });