Bug 1697585 - Ask some tests to wait for a tick in browser_click_event_during_autoscrolling.js r=smaug

Some tests need to wait for a full tick cycle to ensure the expected
input tasks are run.

Differential Revision: https://phabricator.services.mozilla.com/D110848

toolkit/content/tests/browser/browser_click_event_during_autoscrolling.js

@@ -35,6 +35,16 @@ add_task(async function() {
         });
       }
 
+      function promiseContentTick() {
+        return SpecialPowers.spawn(browser, [], async () => {
+          await new Promise(r => {
+            content.requestAnimationFrame(() => {
+              content.requestAnimationFrame(r);
+            });
+          });
+        });
+      }
+
       let autoScroller;
       function promiseWaitForAutoScrollerOpen() {
         if (autoScroller?.state == "open") {
@@ -169,6 +179,7 @@ add_task(async function() {
           button: 1, // middle button
         });
         await promiseFlushLayoutInContent();
+        await promiseContentTick();
         await eventsInContent.promiseMouseEvents(
           ["mouseup"],
           "At starting autoscrolling"
@@ -302,6 +313,7 @@ add_task(async function() {
           button: aButton,
         });
         await promiseFlushLayoutInContent();
+        await promiseContentTick();
         await eventsInContent.promiseMouseEvents(
           aButton != 2 ? ["mouseup"] : ["mouseup", "contextmenu"],
           aDescription