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

pkg/oauth2/lib/src/client.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 oauth2_client;
 
 import 'dart:async';
-import 'dart:uri';
 
 import 'package:http/http.dart' as http;
 
 import 'authorization_exception.dart';
 import 'credentials.dart';
 import 'expiration_exception.dart';
 import 'utils.dart';
 
 // TODO(nweiz): Add an onCredentialsRefreshed event once we have some event
 // infrastructure.
@@ skipping 119 matching lines @@
       return this;
     });
   }
 
   /// Closes this client and its underlying HTTP client.
   void close() {
     if (_httpClient != null) _httpClient.close();
     _httpClient = null;
   }
 }