Refactor http.Client and http.BaseClient to allow http.Client in type annotations.

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:uri';
 
 // TODO(nweiz): This should be a "package:" import. See issue 6745.
 import '../../../http/lib/http.dart' as http;
@@ skipping 57 matching lines @@
   /// client. This will usually be listed in the authorization server's
   /// OAuth2 API documentation.
   final Uri authorizationEndpoint;
 
   /// A URL provided by the authorization server that this library uses to
   /// obtain long-lasting credentials. This will usually be listed in the
   /// authorization server's OAuth2 API documentation.
   final Uri tokenEndpoint;
 
   /// The HTTP client used to make HTTP requests.
-  http.BaseClient _httpClient;
+  http.Client _httpClient;
 
   /// The URL to which the resource owner will be redirected after they
   /// authorize this client with the authorization server.
   Uri _redirectEndpoint;
 
   /// The scopes that the client is requesting access to.
   List<String> _scopes;
 
   /// An opaque string that users of this library may specify that will be
   /// included in the response query parameters.
   String _stateString;
 
   /// The current state of the grant object. One of [_INITIAL_STATE],
   /// [_AWAITING_RESPONSE_STATE], or [_FINISHED_STATE].
   int _state = _INITIAL_STATE;
 
   /// Creates a new grant.
   ///
   /// [httpClient] is used for all HTTP requests made by this grant, as well as
   /// those of the [Client] is constructs.
   AuthorizationCodeGrant(
       this.identifier,
       this.secret,
       this.authorizationEndpoint,
       this.tokenEndpoint,
-      {http.BaseClient httpClient})
+      {http.Client httpClient})
     : _httpClient = httpClient == null ? new http.Client() : httpClient;
 
   /// Returns the URL to which the resource owner should be redirected to
   /// authorize this client. The resource owner will then be redirected to
   /// [redirect], which should point to a server controlled by the client. This
   /// redirect will have additional query parameters that should be passed to
   /// [handleAuthorizationResponse].
   ///
   /// The specific permissions being requested from the authorization server may
   /// be specified via [scopes]. The scope strings are specific to the
@@ skipping 134 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;
   }
 }