Remove usage of dart:json.

sdk/lib/_internal/pub/test/validator/dependency_test.dart

 // Copyright (c) 2013, 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 'dart:async';
-import 'dart:json' as json;
+import 'dart:convert';
 
 import 'package:http/http.dart' as http;
 import 'package:http/testing.dart';
 import 'package:path/path.dart' as path;
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../../lib/src/entrypoint.dart';
 import '../../lib/src/validator.dart';
 import '../../lib/src/validator/dependency.dart';
 import '../descriptor.dart' as d;
@@ skipping 16 matching lines @@
 /// Sets up a test package with dependency [dep] and mocks a server with
 /// [hostedVersions] of the package available.
 setUpDependency(Map dep, {List<String> hostedVersions}) {
   useMockClient(new MockClient((request) {
     expect(request.method, equals("GET"));
     expect(request.url.path, equals("/api/packages/foo"));
 
     if (hostedVersions == null) {
       return new Future.value(new http.Response("not found", 404));
     } else {
-      return new Future.value(new http.Response(json.stringify({
+      return new Future.value(new http.Response(JSON.encode({
         "name": "foo",
         "uploaders": ["nweiz@google.com"],
         "versions": hostedVersions.map((version) =>
             packageVersionApiMap(packageMap('foo', version))).toList()
       }), 200));
     }
   }));
 
   d.dir(appPath, [
     d.libPubspec("test_pkg", "1.0.0", deps: {"foo": dep})
@@ skipping 109 matching lines @@
           expect(schedulePackageValidation(dependency), completion(
               pairOf(isEmpty, everyElement(isNot(contains("\n  foo:"))))));
         });
 
         integration("if the lockfile doesn't have an entry for the "
             "dependency", () {
           d.dir(appPath, [
             d.libPubspec("test_pkg", "1.0.0", deps: {
               "foo": "any"
             }),
-            d.file("pubspec.lock", json.stringify({
+            d.file("pubspec.lock", JSON.encode({
               'packages': {
                 'bar': {
                   'version': '1.2.3',
                   'source': 'hosted',
                   'description': {
                     'name': 'bar',
                     'url': 'http://pub.dartlang.org'
                   }
                 }
               }
             }))
           ]).create();
 
           expect(schedulePackageValidation(dependency), completion(
               pairOf(isEmpty, everyElement(isNot(contains("\n  foo:"))))));
         });
       });
 
       group('with a lockfile', () {
         integration('and it should suggest a constraint based on the locked '
             'version', () {
           d.dir(appPath, [
             d.libPubspec("test_pkg", "1.0.0", deps: {
               "foo": "any"
             }),
-            d.file("pubspec.lock", json.stringify({
+            d.file("pubspec.lock", JSON.encode({
               'packages': {
                 'foo': {
                   'version': '1.2.3',
                   'source': 'hosted',
                   'description': {
                     'name': 'foo',
                     'url': 'http://pub.dartlang.org'
                   }
                 }
               }
             }))
           ]).create();
 
           expectDependencyValidationWarning('  foo: ">=1.2.3 <2.0.0"');
         });
 
         integration('and it should suggest a concrete constraint if the locked '
             'version is pre-1.0.0', () {
           d.dir(appPath, [
             d.libPubspec("test_pkg", "1.0.0", deps: {
               "foo": "any"
             }),
-            d.file("pubspec.lock", json.stringify({
+            d.file("pubspec.lock", JSON.encode({
               'packages': {
                 'foo': {
                   'version': '0.1.2',
                   'source': 'hosted',
                   'description': {
                     'name': 'foo',
                     'url': 'http://pub.dartlang.org'
                   }
                 }
               }
             }))
           ]).create();
 
           expectDependencyValidationWarning('  foo: ">=0.1.2 <0.1.3"');
         });
       });
     });
   });
 }