Make json-maps implement Map<String, dynamic>.

tests/corelib/json_map_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.
 
 library json_map_test;
 
 import "package:expect/expect.dart";
 import 'dart:convert' show JSON;
 import 'dart:collection' show LinkedHashMap, HashMap;
 
@@ skipping 35 matching lines @@
   map = jsonify({});
   map.addAll({'a': 'b'});
   testAtoB(map);
 
   testOrder(['a', 'b', 'c', 'd', 'e', 'f']);
 
   testProto();
   testToString();
   testConcurrentModifications();
   testType();
-  testNonStringKeys();
   testClear();
 
   testListEntry();
   testMutation();
 }
 
 void testEmpty(Map map) {
   for (int i = 0; i < 2; i++) {
     Expect.equals(0, map.length);
     Expect.isTrue(map.isEmpty);
@@ skipping 226 matching lines @@
   Expect.isTrue(
       throwsCME(() => testKeys(jsonify(map), (map) => map.addAll({'b': 0}))));
   Expect.isTrue(
       throwsCME(() => testValues(jsonify(map), (map) => map.addAll({'b': 0}))));
   Expect.isTrue(throwsCME(
       () => testForEach(jsonify(map), (map) => map.addAll({'b': 0}))));
 }
 
 void testType() {
   Expect.isTrue(jsonify({}) is Map);
-  Expect.isTrue(jsonify({}) is HashMap);
-  Expect.isTrue(jsonify({}) is LinkedHashMap);
-
   Expect.isTrue(jsonify({}) is Map<String, dynamic>);
-  Expect.isTrue(jsonify({}) is HashMap<String, dynamic>);
-  Expect.isTrue(jsonify({}) is LinkedHashMap<String, dynamic>);
-
-  Expect.isTrue(jsonify({}) is Map<int, dynamic>);
-  Expect.isTrue(jsonify({}) is HashMap<int, dynamic>);
-  Expect.isTrue(jsonify({}) is LinkedHashMap<int, dynamic>);
-}
-
-void testNonStringKeys() {
-  Map map = jsonify({});
-  map[1] = 2;
-  Expect.equals(1, map.length);
-  Expect.equals(2, map[1]);
+  Expect.isFalse(jsonify({}) is Map<int, dynamic>);
 }
 
 void testClear() {
   Map map = jsonify({'a': 0});
   map.clear();
   Expect.equals(0, map.length);
 }
 
 void testListEntry() {
   Map map = jsonify({
@@ skipping 11 matching lines @@
 }
 
 void testMutation() {
   Map map = jsonify({'a': 0});
   Expect.listEquals(['a', 0], listEach(map));
   map['a'] = 1;
   Expect.listEquals(['a', 1], listEach(map));
   map['a']++;
   Expect.listEquals(['a', 2], listEach(map));
 }