Merge the dart:uri library into dart:core and update the Uri class

pkg/oauth2/lib/src/authorization_code_grant.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 authorization_code_grant;
 
 import 'dart:async';
-import 'dart:uri';
 
 import 'package:http/http.dart' as http;
 
 import 'client.dart';
 import 'authorization_exception.dart';
 import 'handle_access_token_response.dart';
 import 'utils.dart';
 
 /// A class for obtaining credentials via an [authorization code grant][]. This
 /// method of authorization involves sending the resource owner to the
@@ skipping 230 matching lines @@
   /// Closes the grant and frees its resources.
   ///
   /// This will close the underlying HTTP client, which is shared by the
   /// [Client] created by this grant, so it's not safe to close the grant and
   /// continue using the client.
   void close() {
     if (_httpClient != null) _httpClient.close();
     _httpClient = null;
   }
 }