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

sdk/lib/_internal/compiler/implementation/lib/js_array.dart

Index: sdk/lib/_internal/compiler/implementation/lib/js_array.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/js_array.dart b/sdk/lib/_internal/compiler/implementation/lib/js_array.dart
index 62d7463d25f3f69a86127709a6e57c80a3f29cc9..aa6801b72763225996d732455dccd58397ab7f73 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/js_array.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/js_array.dart
@@ -221,6 +221,8 @@ class JSArray<E> implements List<E> {
 
   bool every(bool f(E element)) => IterableMixinWorkaround.every(this, f);
 
+  List<E> get reversed => new ReversedList<E>(this, 0, length);
+
   void sort([int compare(E a, E b)]) {
     checkMutable(this, 'sort');
     if (compare == null) compare = Comparable.compare;