Add a --reporter flag and expose the expanded reporter.

lib/src/runner/engine.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.runner.engine;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:pool/pool.dart';
@@ skipping 62 matching lines @@
     var controller;
     controller = new LiveTestController(suite, test, () {
       controller.setState(const State(Status.running, Result.success));
       controller.setState(const State(Status.complete, Result.success));
       controller.completer.complete();
     }, () {});
     return controller.liveTest;
   }
 
   /// Creates an [Engine] that will run all tests in [suites].
+  ///
+  /// [concurrency] controls how many suites are run at once.
   Engine(Iterable<Suite> suites, {int concurrency})
       : _liveTestsBySuite = _computeLiveTestsBySuite(suites),
         _pool = new Pool(concurrency == null ? 1 : concurrency);
 
   /// Runs all tests in all suites defined by this engine.
   ///
   /// This returns `true` if all tests succeed, and `false` otherwise. It will
   /// only return once all tests have finished running.
   Future<bool> run() {
     if (_runCalled) {
@@ skipping 25 matching lines @@
   /// engine should release any resources it has allocated.
   ///
   /// Any actively-running tests are also closed. VM tests are allowed to finish
   /// running so that any modifications they've made to the filesystem can be
   /// cleaned up.
   Future close() {
     _closed = true;
     return Future.wait(liveTests.map((liveTest) => liveTest.close()));
   }
 }