Removed syntax error from example.dart.

pkg/args/example.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.
 
 /**
  * This is an example of converting the args in test.dart to use this API.
  * It shows what it looks like to build an [ArgParser] and then, when the code
  * is run, demonstrates what the generated usage text looks like.
  */
 #library('example');
@@ skipping 10 matching lines @@
       allowed: ['all', 'debug', 'release']);
 
   parser.addOption('compiler', abbr: 'c', defaultsTo: 'none',
       help: 'Specify any compilation step (if needed).',
       allowed: ['none', 'dart2js', 'dartc'],
       allowedHelp: {
         'none': 'Do not compile the Dart code (run native Dart code on the'
           ' VM).\n(only valid with the following runtimes: vm, drt)',
         'dart2js': 'Compile dart code to JavaScript by running dart2js.\n'
           '(only valid with the following runtimes: d8, drt, chrome\n'
-          'safari, ie, firefox, opera, none (compile only))'
+          'safari, ie, firefox, opera, none (compile only))',
         'dartc': 'Perform static analysis on Dart code by running dartc.\n'
           '(only valid with the following runtimes: none)',
       });
 
   parser.addOption('runtime', abbr: 'r', defaultsTo: 'vm',
       help: 'Where the tests should be run.',
       allowed: ['vm', 'd8', 'drt', 'dartium', 'ff', 'firefox', 'chrome',
               'safari', 'ie', 'opera', 'none'],
       allowedHelp: {
         'vm': 'Run Dart code on the standalone dart vm.',
@@ skipping 76 matching lines @@
   parser.addOption('dart',    help: 'Path to dart executable');
   parser.addOption('drt',     help: 'Path to DumpRenderTree executable');
   parser.addOption('dartium', help: 'Path to Dartium Chrome executable');
 
   parser.addFlag('batch', abbr: 'b',
       help: 'Run browser tests in batch mode',
       defaultsTo: true);
 
   print(parser.getUsage());
 }