Switch from AsyncThunk to AsyncMemoizer.

lib/src/runner/browser/server.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.browser.server;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:async/async.dart';
 import 'package:http_multi_server/http_multi_server.dart';
 import 'package:path/path.dart' as p;
 import 'package:pool/pool.dart';
 import 'package:shelf/shelf.dart' as shelf;
 import 'package:shelf/shelf_io.dart' as shelf_io;
 import 'package:shelf_static/shelf_static.dart';
 import 'package:shelf_web_socket/shelf_web_socket.dart';
 
 import '../../backend/metadata.dart';
 import '../../backend/suite.dart';
 import '../../backend/test_platform.dart';
-import '../../util/async_thunk.dart';
 import '../../util/io.dart';
 import '../../util/one_off_handler.dart';
 import '../../util/path_handler.dart';
 import '../../util/stack_trace_mapper.dart';
 import '../../utils.dart';
 import '../application_exception.dart';
 import '../load_exception.dart';
 import 'browser.dart';
 import 'browser_manager.dart';
 import 'compiler_pool.dart';
@@ skipping 83 matching lines @@
   /// The pool of active `pub serve` compilations.
   ///
   /// Pub itself ensures that only one compilation runs at a time; we just use
   /// this pool to make sure that the output is nice and linear.
   final _pubServePool = new Pool(1);
 
   /// The HTTP client to use when caching JS files in `pub serve`.
   final HttpClient _http;
 
   /// Whether [close] has been called.
-  bool get _closed => _closeThunk.hasRun;
+  bool get _closed => _closeMemo.hasRun;
 
-  /// The thunk for running [close] exactly once.
-  final _closeThunk = new AsyncThunk();
+  /// The memoizer for running [close] exactly once.
+  final _closeMemo = new AsyncMemoizer();
 
   /// All currently-running browsers.
   ///
   /// These are controlled by [_browserManager]s.
   final _browsers = new Map<TestPlatform, Browser>();
 
   /// A map from browser identifiers to futures that will complete to the
   /// [BrowserManager]s for those browsers, or the errors that occurred when
   /// trying to load those managers.
   ///
@@ skipping 322 matching lines @@
       default:
         throw new ArgumentError("$browser is not a browser.");
     }
   }
 
   /// Closes the server and releases all its resources.
   ///
   /// Returns a [Future] that completes once the server is closed and its
   /// resources have been fully released.
   Future close() {
-    return _closeThunk.run(() async {
+    return _closeMemo.runOnce(() async {
       var futures = _browsers.values.map((browser) => browser.close()).toList();
 
       futures.add(_server.close());
       futures.add(_compilers.close());
 
       await Future.wait(futures);
 
       if (_pubServeUrl == null) {
         new Directory(_compiledDir).deleteSync(recursive: true);
       } else {
         _http.close();
       }
     });
   }
 }