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

runtime/lib/array.dart

Index: runtime/lib/array.dart
diff --git a/runtime/lib/array.dart b/runtime/lib/array.dart
index f72191dfb22b99fdfba04bf3dc9eb1ce523da503..3b457faa494fa798cade62fa09c65d31c9dd88dc 100644
--- a/runtime/lib/array.dart
+++ b/runtime/lib/array.dart
@@ -101,7 +101,7 @@ class _ObjectArray<E> implements List<E> {
   }
 
   Iterable map(f(E element)) {
-    return IterableMixinWorkaround.map(this, f);
+    return IterableMixinWorkaround.mapList(this, f);
   }
 
   List mappedBy(f(E element)) {
@@ -331,7 +331,7 @@ class _ImmutableArray<E> implements List<E> {
   }
 
   Iterable map(f(E element)) {
-    return IterableMixinWorkaround.map(this, f);
+    return IterableMixinWorkaround.mapList(this, f);
   }
 
   List mappedBy(f(E element)) {