Update charted to 0.4.8 and roll

packages/quiver/lib/src/collection/delegates/set.dart

 // Copyright 2013 Google Inc. All Rights Reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
 part of quiver.collection;
 
-/**
- * An implementation of [Set] that delegates all methods to another [Set].
- * For instance you can create a FruitSet like this :
- *
- *     class FruitSet extends DelegatingSet<Fruit> {
- *       final Set<Fruit> _fruits = new Set<Fruit>();
- *
- *       Set<Fruit> get delegate => _fruits;
- *
- *       // custom methods
- *     }
- */
+/// An implementation of [Set] that delegates all methods to another [Set].
+/// For instance you can create a FruitSet like this :
+///
+///     class FruitSet extends DelegatingSet<Fruit> {
+///       final Set<Fruit> _fruits = new Set<Fruit>();
+///
+///       Set<Fruit> get delegate => _fruits;
+///
+///       // custom methods
+///     }
 abstract class DelegatingSet<E> extends DelegatingIterable<E>
     implements Set<E> {
   Set<E> get delegate;
 
   bool add(E value) => delegate.add(value);
 
   void addAll(Iterable<E> elements) => delegate.addAll(elements);
 
   void clear() => delegate.clear();
 
   bool containsAll(Iterable<Object> other) => delegate.containsAll(other);
 
-  Set<E> difference(Set<E> other) => delegate.difference(other);
+  Set<E> difference(Set<Object> other) => delegate.difference(other);
 
   Set<E> intersection(Set<Object> other) => delegate.intersection(other);
 
   E lookup(Object object) => delegate.lookup(object);
 
   bool remove(Object value) => delegate.remove(value);
 
   void removeAll(Iterable<Object> elements) => delegate.removeAll(elements);
 
   void removeWhere(bool test(E element)) => delegate.removeWhere(test);
 
   void retainAll(Iterable<Object> elements) => delegate.retainAll(elements);
 
   void retainWhere(bool test(E element)) => delegate.retainWhere(test);
 
   Set<E> union(Set<E> other) => delegate.union(other);
 }