Remove Collection, Collections and clean up List/Set/Queue implementations of retain/remove.

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> {
+abstract class _HashSetBase<E> extends Iterable<E> implements Set<E> {
   // Set.
-  bool isSubsetOf(Collection<E> other) {
-    // Deprecated, and using old signature.
-    Set otherSet;
-    if (other is Set) {
-      otherSet = other;
-    } else {
-      otherSet = other.toSet();
-    }
-    return otherSet.containsAll(this);
-  }
-
   bool containsAll(Iterable<E> other) {
     for (E object in other) {
       if (!this.contains(object)) return false;
     }
     return true;
   }
 
   /** Create a new Set of the same type as this. */
   Set _newSet();
 
@@ skipping 26 matching lines @@
   void retainAll(Iterable objectsToRetain) {
     Set retainSet;
     if (objectsToRetain is Set) {
       retainSet = objectsToRetain;
     } else {
       retainSet = objectsToRetain.toSet();
     }
     retainWhere(retainSet.contains);
   }
 
-  String toString() => Collections.collectionToString(this);
+  String toString() => ToString.iterableToString(this);
 }
 
 class HashSet<E> extends _HashSetBase<E> {
   external HashSet();
 
   factory HashSet.from(Iterable<E> iterable) {
     return new HashSet<E>()..addAll(iterable);
   }
 
   // Iterable.
@@ skipping 16 matching lines @@
 
   external void removeWhere(bool test(E element));
 
   external void retainWhere(bool test(E element));
 
   external void clear();
 
   // Set.
   Set<E> _newSet() => new HashSet<E>();
 }