Added MappedListIterable/Iterator to implement map() on Lists.

sdk/lib/collection/collections.dart

Index: sdk/lib/collection/collections.dart
diff --git a/sdk/lib/collection/collections.dart b/sdk/lib/collection/collections.dart
index 0c45e21d4250f85f4e04110279d4fb89403f8e76..369a3d3edab79ac00a7d3db1d1bbda6926dd912a 100644
--- a/sdk/lib/collection/collections.dart
+++ b/sdk/lib/collection/collections.dart
@@ -317,6 +317,10 @@ class IterableMixinWorkaround {
     return new MappedIterable(iterable, f);
   }
 
+  static Iterable mapList(List list, f(var element)) {
+    return new MappedListIterable(list, f, 0, null);
+  }
+
   static List mappedByList(List list, f(var element)) {
     // This is currently a List as well as an Iterable.
     return new MappedList(list, f);