Add a LiveSuite class.

test/runner/configuration/top_level_test.dart

 // Copyright (c) 2016, 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.
 
 @TestOn("vm")
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:path/path.dart' as p;
@@ skipping 316 matching lines @@
     d.async(pubServePort.then((port) {
       return d.file("dart_test.yaml", JSON.encode({
         "pub_serve": port
       }));
     })).create();
 
     var test = runTest([]);
     test.stdout.expect(consumeThrough(contains('+1: All tests passed!')));
     test.shouldExit(0);
     pub.kill();
-  });
+  }, tags: 'pub');
 
   test("uses the specified concurrency", () {
     d.file("dart_test.yaml", JSON.encode({
       "concurrency": 2
     })).create();
 
     d.file("test.dart", """
       import 'package:test/test.dart';
 
       void main() {
@@ skipping 187 matching lines @@
           test("failure", () => throw "oh no");
         }
       """)
     ]).create();
 
     var test = runTest([]);
     test.stdout.expect(consumeThrough(contains('All tests passed!')));
     test.shouldExit(0);
   });
 }