Upstream Service Worker window test to WPT

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

-self.addEventListener('message', function(event) {
-    event.waitUntil(self.clients.claim()
-      .then(function(result) {
-          if (result !== undefined) {
-              event.data.port.postMessage(
-                  'FAIL: claim() should be resolved with undefined');
-              return;
-          }
-          event.data.port.postMessage('PASS');
-        })
-      .catch(function(error) {
-          event.data.port.postMessage('FAIL: exception: ' + error.name);
-        }));
-  });