Switch from AsyncThunk to AsyncMemoizer.

lib/src/runner/loader.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.loader;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
 
 import 'package:analyzer/analyzer.dart';
+import 'package:async/async.dart';
 import 'package:path/path.dart' as p;
 import 'package:stack_trace/stack_trace.dart';
 
 import '../backend/invoker.dart';
 import '../backend/metadata.dart';
 import '../backend/test_platform.dart';
-import '../util/async_thunk.dart';
 import '../util/dart.dart' as dart;
 import '../util/io.dart';
 import '../util/remote_exception.dart';
 import '../utils.dart';
 import 'browser/server.dart';
 import 'load_exception.dart';
 import 'load_suite.dart';
 import 'parse_metadata.dart';
 import 'runner_suite.dart';
 import 'vm/isolate_test.dart';
@@ skipping 24 matching lines @@
   /// This is `null` if tests should be loaded from the filesystem.
   final Uri _pubServeUrl;
 
   /// All suites that have been created by the loader.
   final _suites = new Set<RunnerSuite>();
 
   /// The server that serves browser test pages.
   ///
   /// This is lazily initialized the first time it's accessed.
   Future<BrowserServer> get _browserServer {
-    return _browserServerThunk.run(() {
+    return _browserServerMemo.runOnce(() {
       return BrowserServer.start(
           root: _root,
           packageRoot: _packageRoot,
           pubServeUrl: _pubServeUrl,
           color: _color,
           jsTrace: _jsTrace);
     });
   }
-  final _browserServerThunk = new AsyncThunk<BrowserServer>();
+  final _browserServerMemo = new AsyncMemoizer<BrowserServer>();
 
-  /// The thunk for running [close] exactly once.
-  final _closeThunk = new AsyncThunk();
+  /// The memoizer for running [close] exactly once.
+  final _closeMemo = new AsyncMemoizer();
 
   /// Creates a new loader.
   ///
   /// [root] is the root directory that will be served for browser tests. It
   /// defaults to the working directory.
   ///
   /// If [packageRoot] is passed, it's used as the package root for all loaded
   /// tests. Otherwise, it's inferred from [root].
   ///
   /// If [pubServeUrl] is passed, tests will be loaded from the `pub serve`
@@ skipping 187 matching lines @@
           onClose: isolate.kill);
       _suites.add(suite);
       return suite;
     } finally {
       subscription.cancel();
     }
   }
 
   /// Closes the loader and releases all resources allocated by it.
   Future close() {
-    return _closeThunk.run(() async {
+    return _closeMemo.runOnce(() async {
       await Future.wait(_suites.map((suite) => suite.close()));
       _suites.clear();
 
-      if (!_browserServerThunk.hasRun) return;
+      if (!_browserServerMemo.hasRun) return;
       await (await _browserServer).close();
     });
   }
 }