Suppress get_drt/dartium download if an executable is provided via flag

tools/testing/dart/test_options.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.
 
 #library("test_options_parser");
 
 #import("dart:io");
 #import("dart:builtin");
 #import("drt_updater.dart");
 
@@ skipping 500 matching lines @@
     if (configuration['compiler'].contains(',')) {
       return _expandHelper('compiler', configuration);
     }
 
     // Expand runtimes.
     var runtimes = configuration['runtime'];
     if (runtimes.contains(',')) {
       return _expandHelper('runtime', configuration);
     } else {
       // All runtimes eventually go through this path, after expansion.
-      var updater = runtimeUpdater(runtimes);
+      var updater = runtimeUpdater(configuration);
       if (updater !== null) {
         updater.update();
       }
     }
 
     // Adjust default timeout based on mode, compiler, and sometimes runtime.
     if (configuration['timeout'] == -1) {
       var timeout = 60;
       switch (configuration['compiler']) {
         case 'dartc':
@@ skipping 96 matching lines @@
         return option;
       }
     }
     print('Unknown test option $name');
     exit(1);
   }
 
 
   List<_TestOptionSpecification> _options;
 }