Use List instead of Link in the type system.

tests/compiler/dart2js/link_helper.dart

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library link_helper;
+import '../../../sdk/lib/_internal/compiler/implementation/util/util.dart';
+import '../../../sdk/lib/_internal/compiler/implementation/util/util_implementation.dart';
+
+Link LinkFromList(List list) {
+  switch (list.length) {
+    case 0:
+      return new Link();
+    case 1:
+      return new LinkEntry(list[0]);
+    case 2:
+      return new LinkEntry(list[0], new LinkEntry(list[1]));
+    case 3:
+      return new LinkEntry(
+          list[0], new LinkEntry(list[1], new LinkEntry(list[2])));
+  }
+  Link link = new Link();
+  for (int i = list.length; i > 0; i--) {
+    link = link.prepend(list[i - 1]);
+  }
+  return link;
+}