polymer - 为什么 Polymer cli 元素在演示页面上有 service worker 错误？

Question

当我使用聚合物 cli v0.17.0并运行polymer init然后选择元素时，它会创建一个简单的元素项目。然后我用来polymer serve在浏览器中查看项目。

当我导航到演示页面时，为什么它以 service worker 错误开始？

A bad HTTP response code (404) was received when fetching the script.  :8080/service-worker.js:1 

Failed to load resource: net::ERR_INVALID_RESPONSE  http://localhost:8080/service-worker.js