function track_installing(worker){
  console.log('track_installing called...');
  //if this service worker finished installing, tell it to take over.
  worker.addEventListener('statechange', ()=>{
    if (worker.state === 'installed') {
      update_ready(worker);
    }
  });
}
//create an state change tracker for this service worker
create an state change tracker for this service worker
create an state change tracker for this service worker
function track_installing(worker){
  console.log('track_installing called...');
  worker.addEventListener('statechange', ()=>{
    if (worker.state === 'installed') {
      update_ready(worker);
    }
  });
}
function track_installing ( worker ) { console . log ( 'track_installing called...' ) ; worker . addEventListener ( 'statechange' , ( ) => { if ( worker . state === 'installed' ) { update_ready ( worker ) ; } } ) ; }
create an state change tracker for this service worker
create an state change tracker for this service worker
//if this service worker finished installing, tell it to take over.