Update searchable_list test to run in package bots

lib/searchable_list.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 searchable_list.searchable_list;
 
 import 'package:polymer/polymer.dart';
 
 @CustomTag('searchable-list')
 class SearchableList extends PolymerElement {
   @observable bool applyAuthorStyles = true;
   @observable String searchParam;
   @published List<String> data = [];
   final List<String> results = toObservable([]);
 
   SearchableList.created() : super.created();
 
   attached() {
     super.attached();
     results.addAll(data);
     onPropertyChange(this, #searchParam, search);
   }
 
   search() {
     results.clear();
     String lower = searchParam.toLowerCase();
     results.addAll(data.where((d) => d.toLowerCase().contains(lower)));
   }
 }