Fix typing for lookup-map test.

pkg/lookup_map/test/lookup_map_test.dart

 // Copyright (c) 2015, 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:lookup_map/lookup_map.dart';
 
 import 'package:test/test.dart';
 
 class Key {
   final int id;
@@ skipping 11 matching lines @@
         B, "the-text-for-B",
         1.2, "the-text-for-1.2"]);
     expect(m[A], 'the-text-for-A');
     expect(m[B], 'the-text-for-B');
     expect(m[1.2], 'the-text-for-1.2');
     expect(m[C], null);
     expect(m[1.3], null);
   });
 
   test('pair constructor', () {
-    var m = const LookupMap.pair(A, "the-text-for-A");
+    var m = const LookupMap<dynamic, String>.pair(A, "the-text-for-A");
     expect(m[A], 'the-text-for-A');
     expect(m[B], null);
   });
 
   test('nested lookup', () {
     var m = const LookupMap(const [],
-        const [const LookupMap.pair(A, "the-text-for-A")]);
+        const [const LookupMap<dynamic, String>.pair(A, "the-text-for-A")]);
     expect(m[A], 'the-text-for-A');
     expect(m[B], null);
   });
 
   test('entry shadows nested maps', () {
     var m = const LookupMap(const [
       A, "the-text-for-A2",
     ], const [
       const LookupMap.pair(A, "the-text-for-A1"),
     ]);
@@ skipping 15 matching lines @@
   // sanity.
   test('reachable lookups are not tree-shaken', () {
     var m = const LookupMap(const [
       A, B,
       B, C,
       C, 3.4,
     ]);
     expect(m[m[m[A]]], 3.4);
   });
 }