Add timeout tests for the pool package.

pkg/pool/lib/pool.dart

 // Copyright (c) 2014, 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 pool;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:stack_trace/stack_trace.dart';
@@ skipping 22 matching lines @@
   /// The timeout timer.
   ///
   /// If [_timeout] isn't null, this timer is set as soon as the resource limit
   /// is reached and is reset every time an resource is released or a new
   /// resource is requested. If it fires, that indicates that the caller became
   /// deadlocked, likely due to files waiting for additional files to be read
   /// before they could be closed.
   Timer _timer;
 
   /// The amount of time to wait before timing out the pending resources.
-  Duration _timeout;
+  final Duration _timeout;
 
   /// Creates a new pool with the given limit on how many resources may be
   /// allocated at once.
   ///
   /// If [timeout] is passed, then if that much time passes without any activity
-  /// all pending [request] futures will throw an exception. This is indented
-  /// to avoid deadlocks.
+  /// all pending [request] futures will throw a [TimeoutException]. This is
+  /// intended to avoid deadlocks.
   Pool(this._maxAllocatedResources, {Duration timeout})
       : _timeout = timeout;
 
   /// Request a [PoolResource].
   ///
   /// If the maximum number of resources is already allocated, this will delay
   /// until one of them is released.
   Future<PoolResource> request() {
     if (_allocatedResources < _maxAllocatedResources) {
       _allocatedResources++;
@@ skipping 38 matching lines @@
       _timer = null;
     } else {
       _timer = new Timer(_timeout, _onTimeout);
     }
   }
 
   /// Handles [_timer] timing out by causing all pending resource completers to
   /// emit exceptions.
   void _onTimeout() {
     for (var completer in _requestedResources) {
-      completer.completeError("Pool deadlock: all resources have been "
-          "allocated for too long.", new Chain.current());
+      completer.completeError(
+          new TimeoutException("Pool deadlock: all resources have been "
+              "allocated for too long.",
+              _timeout),
+          new Chain.current());
     }
     _requestedResources.clear();
     _timer = null;
   }
 }
 
 /// A member of a [Pool].
 ///
 /// A [PoolResource] is a token that indicates that a resource is allocated.
 /// When the associated resource is released, the user should call [release].
 class PoolResource {
   final Pool _pool;
 
   /// Whether [this] has been released yet.
   bool _released = false;
 
   PoolResource._(this._pool);
 
   /// Tells the parent [Pool] that the resource associated with this resource is
   /// no longer allocated, and that a new [PoolResource] may be allocated.
   void release() {
     if (_released) {
       throw new StateError("A PoolResource may only be released once.");
     }
     _released = true;
     _pool._onResourceReleased();
   }
 }