Implement JS version of LinkedHashSet and move the various HashTable implementations to the VM coll…

sdk/lib/collection/hash_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.
 
 part of dart.collection;
 
 /** Common parts of [HashSet] and [LinkedHashSet] implementations. */
 abstract class _HashSetBase<E> extends Collection<E> implements Set<E> {
   // Set.
   bool isSubsetOf(Collection<E> other) {
@@ skipping 33 matching lines @@
   }
 
   Set<E> difference(Set<E> other) {
     HashSet<E> result = _newSet();
     for (E element in this) {
       if (!other.contains(element)) result.add(element);
     }
     return result;
   }
 
+  void retainAll(Iterable objectsToRetain) {
+    Set retainSet;
+    if (objectsToRetain is Set) {
+      retainSet = objectsToRetain;
+    } else {
+      retainSet = objectsToRetain.toSet();
+    }
+    retainWhere(retainSet.contains);
+  }
+
   String toString() => Collections.collectionToString(this);
 }
 
 class HashSet<E> extends _HashSetBase<E> {
   external HashSet();
 
   factory HashSet.from(Iterable<E> iterable) {
     return new HashSet<E>()..addAll(iterable);
   }
 
   // Iterable.
   external Iterator<E> get iterator;
 
   external int get length;
 
   external bool get isEmpty;
 
   external bool contains(Object object);
 
   // Collection.
   external void add(E element);
 
   external void addAll(Iterable<E> objects);
 
   external bool remove(Object object);
 
   external void removeAll(Iterable objectsToRemove);
 
-  void retainAll(Iterable objectsToRetain) {
-    Set retainSet;
-    if (objectsToRetain is Set) {
-      retainSet = objectsToRetain;
-    } else {
-      retainSet = objectsToRetain.toSet();
-    }
-    retainWhere(retainSet.contains);
-  }
-
   external void removeWhere(bool test(E element));
 
   external void retainWhere(bool test(E element));
 
   external void clear();
 
   // Set.
   Set<E> _newSet() => new HashSet<E>();
 }