Make List.skip, List.take and List.reversed return Iterables, not Lists.

sdk/lib/core/list.dart

Index: sdk/lib/core/list.dart
diff --git a/sdk/lib/core/list.dart b/sdk/lib/core/list.dart
index 10ba3e054fc25864cae93e793d8731a9376c1b99..ecb5535b50e380640a36a5ca9917836c1ca02ecf 100644
--- a/sdk/lib/core/list.dart
+++ b/sdk/lib/core/list.dart
@@ -77,13 +77,9 @@ abstract class List<E> implements Collection<E> {
   void addAll(Iterable<E> iterable);
 
   /**
-   * Returns a reversed fixed-length view of this [List].
-   *
-   * The reversed list has elements in the opposite order of this list.
-   * It is backed by this list, but will stop working if this list
-   * becomes shorter than its current length.
+   * Returns an [Iterable] of the elements of this [List] in reverse order.
    */
-  List<E> get reversed;
+  Iterable<E> get reversed;
 
   /**
    * Sorts the list according to the order specified by the [compare] function.