Change List.sort to not have a default parameter value.

sdk/lib/core/list.dart

 // Copyright (c) 2012, 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 [List] is an indexable collection with a length. It can be of
  * fixed size or extendable.
  */
 abstract class List<E> implements Collection<E>, Sequence<E> {
   /**
@@ skipping 54 matching lines @@
 
   /**
    * Appends all elements of the [collection] to the end of this list.
    * Extends the length of the list by the number of elements in [collection].
    * Throws an [UnsupportedError] if this list is not
    * extendable.
    */
   void addAll(Collection<E> collection);
 
   /**
-   * Sorts the list according to the order specified by the [Comparator].
+   * Sorts the list according to the order specified by the [compare] function.
+   *
+   * The [compare] function must act as a [Comparator].
+   * The default [List] implementations use [Comparable.compare] if
+   * [compare] is omitted.
    */
-  void sort([Comparator<E> compare = Comparable.compare]);
+  void sort([int compare(E a, E b)]);
 
   /**
    * Returns the first index of [element] in the list.
    *
    * Searches the list from index [start] to the length of the list.
    * The first time an element [:e:] is encountered so that [:e == element:],
    * the index of [:e:] is returned.
    * Returns -1 if [element] is not found.
    */
   int indexOf(E element, [int start = 0]);
@@ skipping 90 matching lines @@
    * not extendable.
    * If [length] is 0, this method does not do anything.
    * If [start] is the length of the list, this method inserts the
    * range at the end of the list.
    * Throws an [ArgumentError] if [length] is negative.
    * Throws an [RangeError] if [start] is negative or if
    * [start] is greater than the length of the list.
    */
   void insertRange(int start, int length, [E initialValue]);
 }