ServiceWorker: Wait for the completion of async tasks on ExtendableMessageEvent

third_party/WebKit/LayoutTests/http/tests/serviceworker/chromium/resources/clients-openwindow.js

 // This helper will setup a small test framework that will use TESTS and run
 // them sequentially and call self.postMessage('quit') when done.
 // This helper also exposes |client|, |postMessage()|, |runNextTestOrQuit()|,
 // |synthesizeNotificationClick()| and |initialize()|.
 importScripts('sw-test-helpers.js');
 importScripts('../../../resources/get-host-info.js');
 
 var TESTS = [
     function testWithNoNotificationClick() {
         clients.openWindow('/').catch(function(e) {
@@ skipping 77 matching lines @@
             clients.openWindow('file:///').catch(function(error) {
                 self.postMessage('openWindow() can not open file scheme');
                 self.postMessage('openWindow() error is: ' + error.name);
             }).then(runNextTestOrQuit);
         });
     },
 ];
 
 self.onmessage = function(e) {
     if (e.data == 'start') {
-        initialize().then(runNextTestOrQuit);
+        e.waitUntil(initialize().then(runNextTestOrQuit));
     } else {
-        initialize().then(function() {
+        e.waitUntil(initialize().then(function() {
             self.postMessage('received unexpected message');
             self.postMessage('quit');
-        });
+        }));
     }
 };