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

pkg/oauth2/lib/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.
 
 /// A client library for authenticating with a remote service via OAuth2 on
 /// behalf of a user, and making authorized HTTP requests with the user's OAuth2
 /// credentials.
 ///
 /// ## Installing ##
 ///
@@ skipping 16 matching lines @@
 /// to give the client an access token. This token serves as proof that the
 /// client has permission to access resources on behalf of the resource owner.
 ///
 /// OAuth2 provides several different methods for the client to obtain
 /// authorization. At the time of writing, this library only supports the
 /// [AuthorizationCodeGrant] method, but further methods may be added in the
 /// future. The following example uses this method to authenticate, and assumes
 /// that the library is being used by a server-side application.
 ///
 ///     import 'dart:io'
-///     import 'dart:uri'
 ///     import 'package:oauth2/oauth2.dart' as oauth2;
 ///
 ///     // These URLs are endpoints that are provided by the authorization
 ///     // server. They're usually included in the server's documentation of its
 ///     // OAuth2 API.
 ///     final authorizationEndpoint =
 ///         Uri.parse("http://example.com/oauth2/authorization");
 ///     final tokenEndpoint =
 ///         Uri.parse("http://example.com/oauth2/token");
 ///     
@@ skipping 68 matching lines @@
 ///
 /// [pub]: http://pub.dartlang.org
 /// [pkg]: http://pub.dartlang.org/packages/oauth2
 library oauth2;
 
 export 'src/authorization_code_grant.dart';
 export 'src/client.dart';
 export 'src/credentials.dart';
 export 'src/authorization_exception.dart';
 export 'src/expiration_exception.dart';