[ServiceWorker] Allow waitUntil to be called multiple times asynchronously

third_party/WebKit/LayoutTests/http/tests/serviceworker/chromium/resources/sw-test-helpers.js

Index: third_party/WebKit/LayoutTests/http/tests/serviceworker/chromium/resources/sw-test-helpers.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/serviceworker/chromium/resources/sw-test-helpers.js b/third_party/WebKit/LayoutTests/http/tests/serviceworker/chromium/resources/sw-test-helpers.js
index 3f81a544f3f02181e3d460f994b63af897902da1..974416ef6011b52bb0ea1d42a82f1694ff2ba290 100644
--- a/third_party/WebKit/LayoutTests/http/tests/serviceworker/chromium/resources/sw-test-helpers.js
+++ b/third_party/WebKit/LayoutTests/http/tests/serviceworker/chromium/resources/sw-test-helpers.js
@@ -61,6 +61,9 @@ self.synthesizeNotificationClick = function() {
 
         var handler = function(e) {
             resolve(e);
+            // To allow waitUntil to be called inside execution of the microtask
+            // enqueued by above resolve function.
+            e.waitUntil(Promise.resolve());

[falken, 2017/05/24 08:24:18]

This is pretty tricky and I'm not sure with this change the tests in
resources/notificationclick-can-focus.js are still testing what they intended to
test.

But I don't have any ideas. I think the people originally involved with this
test are no longer working on service worker.

[leonhsl(Using Gerrit), 2017/05/25 00:16:39]

I believe this change does not change any behavior of those tests using this
synthesizeNotificationClick function.
They are calling waitUntil inside the returned promise's resolver function,
which executes on a microtask after completion of the event handler self's
execution. This is allowed before this CL, but now it's forbidden if has no any
other outstanding extend lifetime promise at that time, so I added such a new
call to waitUntil to ensure that.

             e.notification.close();
             self.removeEventListener('notificationclick', handler);
         };