Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/system/templates/select.html.twig

@@ -0,0 +1,15 @@
+{#
+/**
+ * @file
+ * Default theme implementation for a select element.
+ *
+ * Available variables:
+ * - attributes: HTML attributes for the select tag.
+ * - options: The option element children.
+ *
+ * @see template_preprocess_select()
+ *
+ * @ingroup themeable
+ */
+#}
+<select{{ attributes }}>{{ options }}</select>