Fix JSON tests, re-enable in all cases - 2nd try

tools/test.dart

 #!/usr/bin/env dart
 // Copyright (c) 2013, 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.
 
 /**
  * This file is the entrypoint of the dart test suite.  This suite is used
  * to test:
  *
  *     1. the dart vm
@@ skipping 40 matching lines @@
     new Path('samples'),
     new Path('samples-dev'),
     new Path('tests/benchmark_smoke'),
     new Path('tests/chrome'),
     new Path('tests/compiler/dart2js'),
     new Path('tests/compiler/dart2js_extra'),
     new Path('tests/compiler/dart2js_native'),
     new Path('tests/corelib'),
     new Path('tests/html'),
     new Path('tests/isolate'),
-    new Path('tests/json'),
     new Path('tests/language'),
     new Path('tests/lib'),
     new Path('tests/standalone'),
     new Path('tests/try'),
     new Path('tests/utils'),
     new Path('utils/tests/css'),
     new Path('utils/tests/peg'),
     new Path('sdk/lib/_internal/pub'),
 ];
 
@@ skipping 238 matching lines @@
 void main(List<String> arguments) {
   deleteTemporaryDartDirectories().then((_) {
     var optionsParser = new TestOptionsParser();
     var configurations = optionsParser.parse(arguments);
     if (configurations != null && configurations.length > 0) {
       testConfigurations(configurations);
     }
   });
 }