Don't pass 'runGuarded' flag to `bindCallback`.

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.
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:async/async.dart';
 import 'package:stack_trace/stack_trace.dart';
 
@@ skipping 165 matching lines @@
     _resetTimer();
 
     if (_requestedResources.isNotEmpty) {
       var pending = _requestedResources.removeFirst();
       pending.complete(_runOnRelease(onRelease));
     } else if (isClosed) {
       _closeGroup.add(new Future.sync(onRelease));
       _allocatedResources--;
       if (_allocatedResources == 0) _closeGroup.close();
     } else {
-      _onReleaseCallbacks.add(
-          Zone.current.bindCallback(onRelease, runGuarded: false));
+      _onReleaseCallbacks.add(Zone.current.bindCallback(onRelease));
     }
   }
 
   /// Runs [onRelease] and returns a Future that completes to a resource once an
   /// [onRelease] callback completes.
   ///
   /// Futures returned by [_runOnRelease] always complete in the order they were
   /// created, even if earlier [onRelease] callbacks take longer to run.
   Future<PoolResource> _runOnRelease(onRelease()) {
     new Future.sync(onRelease).then((value) {
@@ skipping 68 matching lines @@
   /// produce additional information later on. For example, an isolate's task
   /// may be complete, but it could still emit asynchronous errors.
   void allowRelease(onRelease()) {
     if (_released) {
       throw new StateError("A PoolResource may only be released once.");
     }
     _released = true;
     _pool._onResourceReleaseAllowed(onRelease);
   }
 }