ServiceWorker: Wait for the completion of async tasks on ExtendableMessageEvent

third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/skip-waiting-installed-worker.js

+// TODO(nhiroki): stop using global states because service workers can be killed
+// at any point (http://crbug.com/558244).
 self.state = 'starting';
 
 self.addEventListener('install', function() {
     self.state = 'installing';
   });
 
 self.addEventListener('activate', function() {
     self.state = 'activating';
   });
 
 self.addEventListener('message', function(event) {
     var port = event.data.port;
     if (self.state !== 'installing') {
       port.postMessage('FAIL: Worker should be waiting in installed state');
       return;
     }
-    self.skipWaiting()
+    event.waitUntil(self.skipWaiting()
       .then(function(result) {
           if (result !== undefined) {
             port.postMessage('FAIL: Promise should be resolved with undefined');
             return;
           }
           if (self.state !== 'activating') {
             port.postMessage(
                 'FAIL: Promise should be resolved after worker activated');
             return;
           }
           port.postMessage('PASS');
         })
       .catch(function(e) {
           port.postMessage('FAIL: unexpected exception: ' + e);
-        });
+        }));
   });