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

sdk/lib/_internal/pub/lib/src/oauth2.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;
 
 import 'dart:async';
 import 'dart:io';
-import 'dart:uri';
 
 import 'package:oauth2/oauth2.dart';
 import 'package:pathos/path.dart' as path;
 
 import 'http.dart';
 import 'io.dart';
 import 'log.dart' as log;
 import 'safe_http_server.dart';
 import 'system_cache.dart';
 import 'utils.dart';
@@ skipping 177 matching lines @@
         response.statusCode = 404;
         response.close();
       }
     });
   })
   .then((client) {
     log.message('Successfully authorized.\n');
     return client;
   });
 }