Remove usage of dart:json.

sdk/lib/_internal/pub/lib/src/source/hosted.dart

 // Copyright (c) 2012, 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 pub.source.hosted;
 
 import 'dart:async';
 import 'dart:io' as io;
-import 'dart:json' as json;
+import "dart:convert";
 
 import 'package:http/http.dart' as http;
 import 'package:path/path.dart' as path;
 
 import '../http.dart';
 import '../io.dart';
 import '../log.dart' as log;
 import '../package.dart';
 import '../pubspec.dart';
 import '../source.dart';
@@ skipping 19 matching lines @@
   }
 
   /// Downloads a list of all versions of a package that are available from the
   /// site.
   Future<List<Version>> getVersions(String name, description) {
     var url = _makeUrl(description,
         (server, package) => "$server/api/packages/$package");
 
     log.io("Get versions from $url.");
     return httpClient.read(url, headers: PUB_API_HEADERS).then((body) {
-      var doc = json.parse(body);
+      var doc = JSON.decode(body);
       return doc['versions']
           .map((version) => new Version.parse(version['version']))
           .toList();
     }).catchError((ex) {
       var parsed = _parseDescription(description);
       _throwFriendlyError(ex, parsed.first, parsed.last);
     });
   }
 
   /// Downloads and parses the pubspec for a specific version of a package that
   /// is available from the site.
   Future<Pubspec> describeUncached(PackageId id) {
     // Request it from the server.
     var url = _makeVersionUrl(id, (server, package, version) =>
         "$server/api/packages/$package/versions/$version");
 
     log.io("Describe package at $url.");
     return httpClient.read(url, headers: PUB_API_HEADERS).then((version) {
-      version = json.parse(version);
+      version = JSON.decode(version);
 
       // TODO(rnystrom): After this is pulled down, we could place it in
       // a secondary cache of just pubspecs. This would let us have a
       // persistent cache for pubspecs for packages that haven't actually
       // been installed.
       return new Pubspec.fromMap(version['pubspec'], systemCache.sources);
     }).catchError((ex) {
       var parsed = _parseDescription(id.description);
       _throwFriendlyError(ex, id, parsed.last);
     });
@@ skipping 182 matching lines @@
   var name = description["name"];
   if (name is! String) {
     throw new FormatException("The 'name' key must have a string value.");
   }
 
   var url = description["url"];
   if (url == null) url = HostedSource.defaultUrl;
 
   return new Pair<String, String>(name, url);
 }