Replace string uses with code units in Json parser.

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 @@
 */
 final TEST_SUITE_DIRECTORIES = [
     new Path('tests/corelib'),
     new Path('tests/coroutine'),
     new Path('tests/ffi'),
     new Path('tests/io'),
     new Path('tests/isolate'),
     new Path('tests/unsorted'),
     new Path('tests/language'),
     new Path('tests/simple_system'),
+    new Path('samples'),
 ];
 
 void testConfigurations(List<Map> configurations) {
   var startTime = new DateTime.now();
   // Extract global options from first configuration.
   var firstConf = configurations[0];
   var maxProcesses = firstConf['tasks'];
   var progressIndicator = firstConf['progress'];
   // TODO(kustermann): Remove this option once the buildbots don't use it
   // anymore.
@@ skipping 214 matching lines @@
   TestUtils.setDartDirUri(Platform.script.resolve('..'));
   deleteTemporaryDartDirectories().then((_) {
     var optionsParser = new TestOptionsParser();
     var configurations = optionsParser.parse(arguments);
     if (configurations != null && configurations.length > 0) {
       testConfigurations(configurations);
     }
   });
 }