Move some core classes to collection library.

pkg/oauth2/test/utils.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 utils;
 
 import 'dart:async';
+import 'dart:collection' show Queue;
 
 import '../../unittest/lib/unittest.dart';
 import '../../http/lib/http.dart' as http;
 import '../../http/lib/testing.dart';
 import '../lib/oauth2.dart' as oauth2;
 
 class ExpectClient extends MockClient {
   final Queue<MockClientHandler> _handlers;
 
   ExpectClient._(MockClientHandler fn)
@@ skipping 57 matching lines @@
 
 /// A matcher for functions that throw ExpirationException.
 const Matcher throwsExpirationException =
     const Throws(isExpirationException);
 
 class _ExpirationException extends TypeMatcher {
   const _ExpirationException() : super("ExpirationException");
   bool matches(item, MatchState matchState) =>
     item is oauth2.ExpirationException;
 }