Upstream service worker `claim` tests to WPT

third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/update-claim-worker.php

-<?php
-header("Cache-Control: no-cache, must-revalidate");
-header("Pragma: no-cache");
-header('Content-Type:application/javascript');
-
-echo '// ', microtime();
-?>
-
-// This no-op fetch handler is necessary to bypass explicitly the no fetch
-// handler optimization by which this service worker script can be skipped.
-addEventListener('fetch', event => {
-    return;
-  });
-
-addEventListener('install', event => {
-    event.waitUntil(self.skipWaiting());
-  });
-
-addEventListener('activate', event => {
-    event.waitUntil(self.clients.claim());
-  });