Add simple Dart tasks

pkg/analyzer/test/src/task/test_all.dart

 // Copyright (c) 2015, 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.src.task;
 
 import 'package:unittest/unittest.dart';
 
+import 'dart_test.dart' as dart_test;
 import 'inputs_test.dart' as inputs_test;
 import 'manager_test.dart' as manager_test;
 import 'model_test.dart' as model_test;
 import 'targets_test.dart' as targets_test;
 
 /// Utility for manually running all tests.
 main() {
   groupSep = ' | ';
   group('task tests', () {
+    dart_test.main();
     inputs_test.main();
     manager_test.main();
     model_test.main();
     targets_test.main();
   });
 }