Move pub/barback's Pool class into its own package.

pkg/pool/lib/pool.dart

Index: pkg/pool/lib/pool.dart
diff --git a/sdk/lib/_internal/pub/lib/src/pool.dart b/pkg/pool/lib/pool.dart
similarity index 94%
rename from sdk/lib/_internal/pub/lib/src/pool.dart
rename to pkg/pool/lib/pool.dart
index 24100ca6c604e6b57973e3d35b21fcaa788b1880..36a29c86dca0951753d3bd7159a6f66f1f3dff4d 100644
--- a/sdk/lib/_internal/pub/lib/src/pool.dart
+++ b/pkg/pool/lib/pool.dart
@@ -1,17 +1,14 @@
-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// 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 barback.pool;
+library pool;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:stack_trace/stack_trace.dart';
 
-import 'utils.dart';
-
-// TODO(nweiz): put this somewhere that it can be shared between packages.
 /// Manages an abstract pool of resources with a limit on how many may be in use
 /// at once.
 ///
@@ -76,7 +73,7 @@ class Pool {
   /// The return value of [callback] is piped to the returned Future.
   Future withResource(callback()) {
     return request().then((resource) =>
-        syncFuture(callback).whenComplete(resource.release));
+        Chain.track(new Future.sync(callback)).whenComplete(resource.release));
   }
 
   /// If there are any pending requests, this will fire the oldest one.
@@ -138,4 +135,5 @@ class PoolResource {
     _released = true;
     _pool._onResourceReleased();
   }
-}
+}
+