[ServiceWorker] Allow waitUntil to be called multiple times asynchronously

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

 function match_query(query_string) {
   return self.location.search.substr(1) == 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);
       });
 }
 
 function navigate_test(e) {
   var port = e.data.port;
   var url = e.data.url;
 
   return clients.matchAll({ includeUncontrolled : true })
     .then(function(client_list) {
         for (var i = 0; i < client_list.length; i++) {
@@ skipping 18 matching lines @@
   // If the query string is "?installing", then do test on installing worker.
   // This is only for in-scope-but-not-controlled test.
   receive_event('install').then(function(e) {
       e.waitUntil(receive_event('message').then(navigate_test));
     });
 } else {
   receive_event('message').then(function(e) {
       e.waitUntil(navigate_test(e));
     });
 }