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

pkg/polymer/test/unbind_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.unbind_test;
 
 import 'dart:async' show Future, scheduleMicrotask;
 import 'dart:html';
 
 @MirrorsUsed(targets: const [Polymer], override: 'polymer.test.unbind_test')
@@ skipping 51 matching lines @@
 // extra beat.
 delay(x) => new Future.delayed(new Duration(milliseconds: 50), () => x);
 
 // TODO(jmesserly): fix this when it's easier to get a private symbol.
 final unboundSymbol = reflectClass(Polymer).declarations.keys
     .firstWhere((s) => MirrorSystem.getName(s) == '_unbound');
 
 _unbound(node) => reflect(node).getField(unboundSymbol).reflectee;
 
 unbindTests() {
-  var xTest = document.query('x-test');
+  var xTest = document.querySelector('x-test');
   xTest.foo = 'bar';
   scheduleMicrotask(Observable.dirtyCheck);
 
   return delay(null).then((_) {
     expect(_unbound(xTest), null, reason:
         'element is bound when inserted');
     expect(xTest.fooWasChanged, true, reason:
         'element is actually bound');
     xTest.remove();
   }).then(delay).then((_) {
@@ skipping 23 matching lines @@
   }).then(delay).then((node) {
     expect(_unbound(node), null, reason:
         'element is bound when manually inserted');
     node.remove();
     return node;
   }).then(delay).then((node) {
     expect(_unbound(node), true, reason:
         'element is unbound when manually removed is called');
   });
 }