title: service worker not loading in offline
body: <p>I'm building a progressive web app and the service worker looks like this:</p>
  
  <pre>
  
      CURRENT_CACHE = 'V3';
      FILES_TO_CACHE = [
          '/index.html',
          '/js/bcheck.js',
          '/js/mss.js',
          '/js/vendor.js'
      ];
  
      console.info('in file');
      self.addEventListener('install', function (event) {
          console.info('installed');
          event.waitUntil(caches.open(CURRENT_CACHE).then(function(cache){
              return cache.addAll(FILES_TO_CACHE);
          }));
      });
      self.addEventListener('activate', function (event) {
          console.info('activated');
          event.waitUntil(caches.keys().then(function (cachesNames) {
              return Promise.all(cachesNames.map(function (cacheName) {
                  if (cacheName !== CURRENT_CACHE) {
                      return caches.delete(cacheName);
                  }
              }))
          }));
      });
  
      self.addEventListener('fetch', function(event) {
          event.respondWith(
              caches.match(event.request)
                  .then(function(response) {
                          // Cache hit - return response
                          if (response) {
                              return response;
                          }
  
                          return fetch(event.request);
                      }
                  )
          );
      });
  
  </pre>
  
  <p>I see that after the installation I get all my files cached, but when I put the server offline and reload nothing works, it like the service is offline and nothing loads. </p>
  
  <p>Thanks for the help</p>
  
  <ul>
  <li>I work with local server HTTP on localhost</li>
  </ul>