Enable co19 dart2js browser tests on content shell (drt)

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 "path.dart";
@@ skipping 636 matching lines @@
         validRuntimes = const ['vm', 'drt', 'dartium',
                                'ContentShellOnAndroid', 'DartiumOnAndroid'];
         break;
     }
     if (!validRuntimes.contains(config['runtime'])) {
       isValid = false;
       print("Warning: combination of compiler '${config['compiler']}' and "
           "runtime '${config['runtime']}' is invalid. "
           "Skipping this combination.");
     }
-    if ((config['runtime'] == 'ie9' || config['runtime'] == 'ie10') &&
-        Platform.operatingSystem != 'windows') {
+    if (config['ie'] && Platform.operatingSystem != 'windows') {
       isValid = false;
       print("Warning cannot run Internet Explorer on non-Windows operating"
           " system.");
     }
     if (config['shard'] < 1 || config['shard'] > config['shards']) {
       isValid = false;
       print("Error: shard index is ${config['shard']} out of "
             "${config['shards']} shards");
     }
 
@@ skipping 221 matching lines @@
         return option;
       }
     }
     print('Unknown test option $name');
     exit(1);
   }
 
 
   List<_TestOptionSpecification> _options;
 }