Fix strong mode errors in dart:io.

runtime/bin/directory_patch.dart

Index: runtime/bin/directory_patch.dart
diff --git a/runtime/bin/directory_patch.dart b/runtime/bin/directory_patch.dart
index f98a52e966e57d77f457de9c00dc2381b9161351..9f4a2657b53d171d295b1a5ac958bfff4e1827d9 100644
--- a/runtime/bin/directory_patch.dart
+++ b/runtime/bin/directory_patch.dart
@@ -13,8 +13,10 @@ patch class _Directory {
       native "Directory_Delete";
   /* patch */ static _rename(String path, String newPath)
       native "Directory_Rename";
-  /* patch */ static List _list(String path, bool recursive, bool followLinks)
-      native "Directory_List";
+  /* patch */ static void _fillWithDirectoryListing(
+      List<FileSystemEntity> list, String path, bool recursive,
+      bool followLinks)
+      native "Directory_FillWithDirectoryListing";
 }
 
 patch class _AsyncDirectoryListerOps {