Make registration.update() no longer force bypassing the HTTP cache (1/2)

LayoutTests/http/tests/serviceworker/ServiceWorkerGlobalScope/resources/update-worker.php

 <?php
-// Force the browser to cache this script. update() should always bypass this
-// cache and fetch a new version.
-header('Cache-Control: max-age=86400');
+// update() does not bypass cache so set the max-age to 0 such that update()
+// can find a new version in the network.
+header('Cache-Control: max-age=0');
 
 // Return a different script for each access.
 header('Content-Type:application/javascript');
 echo '// ' . microtime();
 ?>
 
 importScripts('../../resources/test-helpers.js');
 importScripts('../../resources/worker-testharness.js');
 
 var events_seen = [];
@@ skipping 11 matching lines @@
     e.respondWith(new Response(events_seen));
   });
 
 self.addEventListener('message', function(e) {
     events_seen.push('message');
     self.registration.update();
   });
 
 // update() during the script evaluation should be ignored.
 self.registration.update();