List.unmodifiable

tool/input_sdk/lib/internal/list.dart

Index: tool/input_sdk/lib/internal/list.dart
diff --git a/tool/input_sdk/lib/internal/list.dart b/tool/input_sdk/lib/internal/list.dart
index 3e87762c317d2dfd1f93a16e81e2868126809f24..36322034efa5cac3b53040fe9d81e483b45c3c00 100644
--- a/tool/input_sdk/lib/internal/list.dart
+++ b/tool/input_sdk/lib/internal/list.dart
@@ -361,7 +361,7 @@ abstract class NonGrowableListError {
  * That means that it is a destructive conversion.
  * The original list should not be used afterwards.
  *
- * The returned list may be the same list as the orginal,
+ * The returned list may be the same list as the original,
  * or it may be a different list (according to [identical]).
  * The original list may have changed type to be a fixed list,
  * or become empty or been otherwise modified.
@@ -373,4 +373,21 @@ abstract class NonGrowableListError {
  * conversion, at the cost of leaving the original list in an unspecified
  * state.
  */
-external List makeListFixedLength(List growableList);
+external List/*<E>*/ makeListFixedLength/*<E>*/(List/*<E>*/ growableList);
+
+/**
+ * Converts a fixed-length list to an unmodifiable list.
+ *
+ * For internal use only.
+ * Only works for core fixed-length lists as created by `new List(length)`,
+ * or as returned by [makeListFixedLength].
+ *
+ * The operation is efficient. It doesn't copy the elements, but converts
+ * the existing list directly to a fixed length list.
+ * That means that it is a destructive conversion.
+ * The original list should not be used afterwards.
+ *
+ * The unmodifiable list type is similar to the one used by const lists.
+ */
+external List/*<E>*/ makeFixedListUnmodifiable/*<E>*/(
+    List/*<E>*/ fixedLengthList);