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

pkg/polymer/test/prop_attr_reflection_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:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 import 'package:polymer/polymer.dart';
 
@@ skipping 34 matching lines @@
   useHtmlConfiguration();
 
   setUp(() => Polymer.onReady);
 
   // Most tests use @CustomTag, here we test out the impertive register:
   Polymer.register('x-foo', XFoo);
   Polymer.register('x-bar', XBar);
   Polymer.register('x-compose', XCompose);
 
   test('property attribute reflection', () {
-    var xcompose = query('x-compose');
-    var xfoo = query('x-foo');
-    var xbar = query('x-bar');
+    var xcompose = querySelector('x-compose');
+    var xfoo = querySelector('x-foo');
+    var xbar = querySelector('x-bar');
     xfoo.foo = 5;
     return onAttributeChange(xfoo).then((_) {
       expect(xcompose.$['bar'].attributes.containsKey('zim'), false,
           reason: 'attribute bound to property updates when binding is made');
 
       expect('${xfoo.foo}', xfoo.attributes['foo'],
           reason: 'attribute reflects property as string');
       xfoo.attributes['foo'] = '27';
       // TODO(jmesserly): why is JS leaving this as a String? From the code it
       // looks like it should use the type of 5 and parse it as a number.
@@ skipping 42 matching lines @@
       expect(xbar.attributes.containsKey('zim'), false, reason:
           'attribute reflects false valued boolean property as NOT '
           'having attribute');
       xbar.obj = 'hi';
     }).then((_) => onAttributeChange(xbar)).then((_) {
       expect(xbar.attributes['obj'], 'hi', reason:
           'reflect property based on current type');
     });
   });
 }