Bug 1541630 [wpt PR 16142] - Use step_timeout() to force spin the EventLoop, a=testonly

Automatic update from web-platform-tests
Use step_timeout() to force spin the EventLoop (#16142)

Use step_timeout() to force spin the EventLoop. Also allow eventPromise to reject before acceptPromise resolves.

--

wpt-commits: 3bfdeb8976fc51748935c8d1f1014dfba8e08dfb
wpt-pr: 16142

testing/web-platform/tests/payment-request/PaymentRequestUpdateEvent/updateWith-call-immediate-manual.https.html

@@ -55,26 +55,29 @@ function testImmediateUpdate({ textContent: testName }) {
     const eventPromise = new Promise((resolve, reject) => {
       request.addEventListener(
         "shippingaddresschange",
-        async ev => {
-          // spin the event loop, sets [[waitForUpdate]] to true.
-          await Promise.resolve();
-          try {
-            ev.updateWith(validDetails);
-            resolve(); // This is bad.
-          } catch (err) {
-            reject(err); // this is good.
-          }
+        ev => {
+          // Forces updateWith() to be run in the next event loop tick so that
+          // [[waitForUpdate]] is already true when it runs.
+          t.step_timeout(() => {
+            try {
+              ev.updateWith(validDetails);
+              resolve(); // This is bad.
+            } catch (err) {
+              reject(err); // this is good.
+            }
+          });
         },
         { once: true }
       );
     });
-    const response = await request.show();
+    const acceptPromise = request.show();
     await promise_rejects(
       t,
       "InvalidStateError",
       eventPromise,
       "The event loop already spun, so [[waitForUpdate]] is now true"
     );
+    const response = await acceptPromise;
     await response.complete();
   }, testName.trim());
 }