Get rid of all the library tags.

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 oauth2.credentials;
-
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 
 import 'package:http/http.dart' as http;
 
 import 'handle_access_token_response.dart';
 import 'utils.dart';
 
 /// Credentials that prove that a client is allowed to access a resource on the
@@ skipping 193 matching lines @@
     // we should re-use the one we already have.
     if (credentials.refreshToken != null) return credentials;
     return new Credentials(
         credentials.accessToken,
         refreshToken: this.refreshToken,
         tokenEndpoint: credentials.tokenEndpoint,
         scopes: credentials.scopes,
         expiration: credentials.expiration);
   }
 }