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

pkg/oauth2/lib/src/credentials.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 credentials;
 
 import 'dart:json';
 import 'dart:uri';
 
 import '../../../http/lib/http.dart' as http;
@@ skipping 126 matching lines @@
   /// You may request different scopes than the default by passing in
   /// [newScopes]. These must be a subset of [scopes].
   ///
   /// This will throw a [StateError] if these credentials can't be refreshed, an
   /// [AuthorizationException] if refreshing the credentials fails, or a
   /// [FormatError] if the authorization server returns invalid responses.
   Future<Credentials> refresh(
       String identifier,
       String secret,
       {List<String> newScopes,
-       http.BaseClient httpClient}) {
+       http.Client httpClient}) {
     var scopes = this.scopes;
     if (newScopes != null) scopes = newScopes;
     if (scopes == null) scopes = <String>[];
     if (httpClient == null) httpClient = new http.Client();
 
     var startTime = new Date.now();
     return async.chain((_) {
       if (refreshToken == null) {
         throw new StateError("Can't refresh credentials without a refresh "
             "token.");
@@ skipping 23 matching lines @@
       if (credentials.refreshToken != null) return credentials;
       return new Credentials(
           credentials.accessToken,
           this.refreshToken,
           credentials.tokenEndpoint,
           credentials.scopes,
           credentials.expiration);
     });
   }
 }