pkg/polymer[_expressions] unittest fixes

pkg/polymer/test/entered_view_test.dart

 // Copyright (c) 2013, 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 polymer.test.entered_view_test;
 
 import 'dart:async';
 import 'dart:html';
 import 'package:polymer/polymer.dart';
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
-import 'package:unittest/matcher.dart';
 
 @reflectable
 class XOuter extends PolymerElement {
   @observable bool expand = false;
 
   XOuter.created() : super.created();
 }
 
 @reflectable
 class XInner extends PolymerElement {
@@ skipping 21 matching lines @@
     return outer.onMutation(outer.shadowRoot).then((_) {
       // Element upgrade is also using mutation observers. Wait another tick so
       // it goes before we do.
       return new Future(() {
         XInner inner = outer.shadowRoot.querySelector('x-inner');
         expect(inner.enteredCount, 1, reason: 'enteredView should be called');
       });
     });
   });
 }