[ServiceWorker] Allow waitUntil to be called multiple times asynchronously

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

Index: third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/windowclient-navigate-worker.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/windowclient-navigate-worker.js b/third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/windowclient-navigate-worker.js
index 09b7724613d25acac74c9fdeed73b1c9be1ac87e..10e86d357cb69a811d90732e07f09b1b51f9d4b8 100644
--- a/third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/windowclient-navigate-worker.js
+++ b/third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/windowclient-navigate-worker.js
@@ -4,7 +4,13 @@ function match_query(query_string) {
 
 function receive_event(event_name) {
   return new Promise(function(resolve) {
-        self.addEventListener(event_name, resolve, false);
+        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]

ditto: this is tricky and i'm not sure what the implications are for the tests
that use this.

+        };
+        self.addEventListener(event_name, handler, false);
       });
 }