Remove usage of dart:json.

sdk/lib/_internal/pub/lib/src/http.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.
 
 /// Helpers for dealing with HTTP.
 library pub.http;
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
-import 'dart:json' as json;
 
 import 'package:http/http.dart' as http;
 
 import 'io.dart';
 import 'log.dart' as log;
 import 'oauth2.dart' as oauth2;
 import 'sdk.dart' as sdk;
 import 'utils.dart';
 
 // TODO(nweiz): make this configurable
@@ skipping 175 matching lines @@
     invalidServerResponse(response);
   }
   throw errorMap['error']['message'];
 }
 
 /// Parses a response body, assuming it's JSON-formatted. Throws a user-friendly
 /// error if the response body is invalid JSON, or if it's not a map.
 Map parseJsonResponse(http.Response response) {
   var value;
   try {
-    value = json.parse(response.body);
+    value = JSON.decode(response.body);
   } on FormatException catch (e) {
     invalidServerResponse(response);
   }
   if (value is! Map) invalidServerResponse(response);
   return value;
 }
 
 /// Throws an error describing an invalid response from the server.
 void invalidServerResponse(http.Response response) =>
   fail('Invalid server response:\n${response.body}');
 
 /// Exception thrown when an HTTP operation fails.
 class PubHttpException implements Exception {
   final http.Response response;
 
   const PubHttpException(this.response);
 
   String toString() => 'HTTP error ${response.statusCode}: '
       '${response.reasonPhrase}';
 }