[gatsby] don't run service-workers outside of https or localhost

see: gatsbyjs#3385

packages/gatsby/cache-dir/app.js

@@ -24,7 +24,7 @@ apiRunnerAsync(`onClientEntry`).then(() => {
  *
  * Let's unregister the service workers in development, and tidy up a few errors.
  */
- if (`serviceWorker` in navigator) {
+ if (supportsServiceWorkers(location, navigator)) {
  navigator.serviceWorker.getRegistrations().then(registrations => {
  for (let registration of registrations) {
  registration.unregister()
@@ -69,3 +69,10 @@ apiRunnerAsync(`onClientEntry`).then(() => {
  })
  }
 })
+
+function supportsServiceWorkers(location, navigator){
+ if (location.hostname === `localhost` || location.protocol === `https:`){
+ return `serviceWorker` in navigator
+ }
+ return false
+}