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

pkg/polymer/test/property_change_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.property_change_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';
 
 // Dart note: this is a tad different from the JS code. We don't support putting
 // expandos on Dart objects and then observing them. On the other hand, we want
 // to make sure that superclass observers are correctly detected.
 
 final _zonk = new Completer();
@@ skipping 30 matching lines @@
 
 main() {
   initPolymer();
   useHtmlConfiguration();
 
   setUp(() => Polymer.onReady);
 
   test('bar change detected', () => _bar.future);
   test('zonk change detected', () => _zonk.future);
 }