Add --dart2js-options flag to test command

tools/testing/dart/test_options.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.
 
 library test_options_parser;
 
 import "dart:io";
 import "drt_updater.dart";
 import "test_suite.dart";
 import "compiler_configuration.dart" show CompilerConfiguration;
@@ skipping 402 matching lines @@
               ['--builder-tag'],
               [],
               ''),
           new _TestOptionSpecification(
               'vm_options',
               'Extra options to send to the vm when running',
               ['--vm-options'],
               [],
               null),
           new _TestOptionSpecification(
+              'dart2js_options',
+              'Extra options for dart2js compilation step',
+              ['--dart2js-options'],
+              [],
+              null),
+          new _TestOptionSpecification(
               'exclude_suite',
               'Exclude suites from default selector, only works when no'
               ' selector has been specified on the command line',
               ['--exclude-suite'],
               defaultTestSelectors,
               null),];
   }
 
 
   /**
@@ skipping 414 matching lines @@
         return option;
       }
     }
     print('Unknown test option $name');
     exit(1);
   }
 
 
   List<_TestOptionSpecification> _options;
 }