Move Iterable implementation to collection.

sdk/lib/core/collection.dart

 // Copyright (c) 2011, 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.core;
 
 /**
  * A collection of individual elements.
  *
  * A [Collection] contains some elements in a structure optimized
  * for certain operations. Different collections are optimized for different
  * uses.
  *
  * A collection can be updated by adding or removing elements.
  *
  * Collections are [Iterable]. The order of iteration is defined by
  * each type of collection.
  *
  * *Deprecated*: This class is deprecated and will be removed soon.
  */
-abstract class Collection<E> extends Iterable<E> {
+abstract class Collection<E> extends IterableBase<E> {
   const Collection();
 
   /**
    * Adds an element to this collection.
    */
   void add(E element);
 
   /**
    * Adds all of [elements] to this collection.
    *
@@ skipping 55 matching lines @@
     IterableMixinWorkaround.retainWhere(this, test);
   }
 
   /**
    * Removes all elements of this collection.
    */
   void clear() {
     IterableMixinWorkaround.removeWhere(this, (E e) => true);
   }
 }