Use List instead of Link in the type system.

tests/compiler/dart2js/link_test.dart

 // Copyright (c) 2011, 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.
 
 import "package:expect/expect.dart";
 import '../../../sdk/lib/_internal/compiler/implementation/util/util.dart';
-import '../../../sdk/lib/_internal/compiler/implementation/util/util_implementation.dart';
+import 'link_helper.dart';
 
 main() {
   test(const Link<Comparable>().prepend('three').prepend(2).prepend('one'),
        ['one', 2, 'three']);
   test(const Link<Comparable>().prepend(3).prepend('two').prepend(1),
        [1, 'two', 3]);
   test(const Link<String>().prepend('single'), ['single']);
   test(const Link(), []);
-  testFromList([]);
-  testFromList([0]);
-  testFromList([0, 1]);
-  testFromList([0, 1, 2]);
-  testFromList([0, 1, 2, 3]);
-  testFromList([0, 1, 2, 3, 4]);
-  testFromList([0, 1, 2, 3, 4, 5]);
   testSkip();
 }
 
-testFromList(List list) {
-  test(new Link.fromList(list), list);
-}
-
 test(Link link, List list) {
   Expect.equals(list.isEmpty, link.isEmpty);
   int i = 0;
   for (var element in link.toList()) {
     Expect.equals(list[i++], element);
   }
   Expect.equals(list.length, i);
   i = 0;
   for (var element in link) {
     Expect.equals(list[i++], element);
   }
   Expect.equals(list.length, i);
   i = 0;
   for (; !link.isEmpty; link = link.tail) {
     Expect.equals(list[i++], link.head);
   }
   Expect.equals(list.length, i);
   Expect.isTrue(link.isEmpty);
 }
 
 testSkip() {
-  var nonEmptyLink = new Link.fromList([0, 1, 2, 3, 4, 5]);
+  var nonEmptyLink = LinkFromList([0, 1, 2, 3, 4, 5]);
   for (int i = 0 ; i < 5; i++) {
     var link = nonEmptyLink.skip(i);
     Expect.isFalse(link.isEmpty);
     Expect.equals(i, link.head);
   }
   Expect.isTrue(nonEmptyLink.skip(6).isEmpty);
   Expect.throws(() => nonEmptyLink.skip(7), (e) => e is RangeError);
 
   var emptyLink = const Link();
   Expect.isTrue(emptyLink.skip(0).isEmpty);
   Expect.throws(() => emptyLink.skip(1), (e) => e is RangeError);
 }