Add List.first.

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.
  */
 interface List<E> extends Collection<E>, Sequence<E>
                   default _ListImpl<E> {
@@ skipping 105 matching lines @@
   E removeAt(int index);
 
   /**
    * Pops and returns the last element of the list.
    * Throws a [UnsupportedError] if the length of the
    * list cannot be changed.
    */
   E removeLast();
 
   /**
+   * Returns the first element of the list, or throws an out of bounds
+   * exception if the list is empty.
+   */
+  E get first;
+
+  /**
    * Returns the last element of the list, or throws an out of bounds
    * exception if the list is empty.
    */
   E get last;
 
   /**
    * Returns a new list containing [length] elements from the list,
    * starting at  [start].
    * Returns an empty list if [length] is 0.
    * Throws an [ArgumentError] if [length] is negative.
@@ skipping 48 matching lines @@
   external factory List([int length]);
 
   /**
    * Factory implementation of List.from().
    *
    * Creates a list with the elements of [other]. The order in
    * the list will be the order provided by the iterator of [other].
    */
   external factory List.from(Iterable<E> other);
 }