[polymer] fix editor hints -- query/queryAll and unused imports

pkg/polymer/test/template_distribute_dynamic_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.
 
 import 'dart:async';
 import 'dart:html';
 import 'package:polymer/polymer.dart';
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 
@@ skipping 40 matching lines @@
     });
   }
 }
 
 main() {
   initPolymer();
   useHtmlConfiguration();
 
   setUp(() => Polymer.onReady);
 
-  test('inserted called', () => (query('x-test') as XTest).onTestDone);
+  test('inserted called', () => (querySelector('x-test') as XTest).onTestDone);
 }