Convert most interfaces in dart:core to abstract classes.

lib/core/queue.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.
 
 /**
  * A [Queue] is a collection that can be manipulated at both ends. One
  * can iterate over the elements of a queue through [forEach] or with
  * an [Iterator].
  */
-interface Queue<E> extends Collection<E> default DoubleLinkedQueue<E> {
+abstract class Queue<E> extends Collection<E> {
 
   /**
    * Creates a queue.
    */
-  Queue();
+  factory Queue() => new DoubleLinkedQueue<E>();
 
   /**
    * Creates a queue with the elements of [other]. The order in
    * the queue will be the order provided by the iterator of [other].
    */
-  Queue.from(Iterable<E> other);
+  factory Queue.from(Iterable<E> other) => new DoubleLinkedQueue<E>.from(other);
 
   /**
    * Removes and returns the first element of this queue. Throws an
    * [EmptyQueueException] exception if this queue is empty.
    */
   E removeFirst();
 
   /**
    * Removes and returns the last element of the queue. Throws an
    * [EmptyQueueException] exception if this queue is empty.
@@ skipping 31 matching lines @@
    * Returns the last element of the queue. Throws an
    * [EmptyQueueException] exception if this queue is empty.
    */
   E last();
 
   /**
    * Removes all elements in the queue. The size of the queue becomes zero.
    */
   void clear();
 }