Add List.reversed to give a reverse fixed-length view of a list.

tests/corelib/list_reversed_test.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.
+
+
+main() {
+  testOperations();
+}
+
+void testOperations() {
+  // Comparison lists.
+  List l = const [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+  List r = const [10, 9, 8, 7, 6, 5, 4, 3, 2, 1];
+  // A base list that starts out like l.
+  List base = l.toList();
+  // A lazy reverse of base.
+  List reversed = base.reversed;
+
+  Expect.listEquals(r, reversed);
+  Expect.listEquals(l, reversed.reversed);
+  for (int i = 0; i < r.length; i++) {
+    Expect.equals(r[i], reversed[i]);
+  }
+  Expect.equals(4, base.indexOf(5));
+  Expect.equals(5, reversed.indexOf(5));
+
+  // Updates write through.
+  for (int i = 0; i < reversed.length; i++) {
+    reversed[i] = l[i];
+  }
+  Expect.listEquals(reversed, l);
+  Expect.listEquals(base, r);
+
+  reversed.setRange(0, r.length, r);
+  Expect.listEquals(reversed, r);
+  Expect.listEquals(base, l);
+
+  reversed.sort();
+  Expect.listEquals(reversed, l);
+  Expect.listEquals(base, r);
+  reversed.setRange(0, r.length, r);
+
+  // Combinations of start and end relative to start/end of list.
+  List subr = [8, 7, 6, 5, 4, 3];
+  Expect.listEquals(subr, reversed.skip(2).take(6));
+  Expect.listEquals(subr, reversed.take(8).skip(2));
+  Expect.listEquals(subr, reversed.reversed.skip(2).take(6).reversed);
+  Expect.listEquals(subr, reversed.reversed.take(8).skip(2).reversed);
+  Expect.listEquals(subr, reversed.take(8).reversed.take(6).reversed);
+  Expect.listEquals(subr, reversed.reversed.take(8).reversed.take(6));
+  Expect.listEquals(subr, reversed.reversed.skip(2).reversed.skip(2));
+  Expect.listEquals(subr, reversed.skip(2).reversed.skip(2).reversed);
+
+  // Reverse const list.
+  Expect.listEquals(r, l.reversed);
+}