Roll to pickup pool changes

packages/barback/lib/src/asset/asset_set.dart

 // Copyright (c) 2013, 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.asset.asset_set;
 
 import 'dart:collection';
 
 import 'asset.dart';
 import 'asset_id.dart';
@@ skipping 19 matching lines @@
       _assets[asset.id] = asset;
     }
   }
 
   Iterator<Asset> get iterator => _assets.values.iterator;
 
   int get length => _assets.length;
 
   /// Gets the [Asset] in the set with [id], or returns `null` if no asset with
   /// that ID is present.
-  Asset operator[](AssetId id) => _assets[id];
+  Asset operator [](AssetId id) => _assets[id];
 
   /// Adds [asset] to the set.
   ///
   /// If there is already an asset with that ID in the set, it is replaced by
   /// the new one. Returns [asset].
   Asset add(Asset asset) {
     _assets[asset.id] = asset;
     return asset;
   }
 
@@ skipping 13 matching lines @@
   /// If the set contains an [Asset] with [id], removes and returns it.
   Asset removeId(AssetId id) => _assets.remove(id);
 
   /// Removes all assets from the set.
   void clear() {
     _assets.clear();
   }
 
   String toString() => _assets.toString();
 }