Fix the popover-events.html failure in wpt.fyi.

At D176675, we replaced the call of waitForRender() with waitForTick() due
to Intermittent result for the test(Bug 1828826). However, wpt.fyi result (which
is now available after we enabled nightly) shows that the test fails.

Reverting waitForTick() to waitForRender() seems fix the issue at wpt.fyi.
A follow-up patch might be needed to update .ini expectation file if there is
intermittent compalins from Gecko run.

Differential Revision: https://phabricator.services.mozilla.com/D195091

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1867486
gecko-commit: e1af579f3385dd2aac37a6f13fa461de05c14f3f
gecko-reviewers: emilio

html/semantics/popovers/popover-events.html

@@ -86,7 +86,7 @@
       assert_equals(0,hideCount);
       assert_equals(0,afterShowCount);
       assert_equals(0,afterHideCount);
-      await waitForTick();
+      await waitForRender();
       assert_equals(1,afterShowCount,'toggle show is fired asynchronously');
       assert_equals(0,afterHideCount);
       assert_true(popover.matches(':popover-open'));
@@ -96,12 +96,12 @@
       assert_equals(1,hideCount);
       assert_equals(1,afterShowCount);
       assert_equals(0,afterHideCount);
-      await waitForTick();
+      await waitForRender();
       assert_equals(1,afterShowCount);
       assert_equals(1,afterHideCount,'toggle hide is fired asynchronously');
       // No additional events
-      await waitForTick();
-      await waitForTick();
+      await waitForRender();
+      await waitForRender();
       assert_false(popover.matches(':popover-open'));
       assert_equals(1,showCount);
       assert_equals(1,hideCount);
@@ -139,8 +139,8 @@
     assert_true(popover.matches(':popover-open'));
     t.add_cleanup(() => {document.body.appendChild(popover);});
     popover.remove();
-    await waitForTick(); // Check for async events also
-    await waitForTick(); // Check for async events also
+    await waitForRender(); // Check for async events also
+    await waitForRender(); // Check for async events also
     assert_false(popover.matches(':popover-open'));
   }, 'The "beforetoggle" event is not fired for element removal');
 
@@ -188,27 +188,27 @@
     assertOnly('none');
     assert_false(popover.matches(':popover-open'));
     popover.showPopover();
-    await waitForTick();
+    await waitForRender();
     assert_true(popover.matches(':popover-open'));
     assertOnly('singleShow','Single event should have been fired, which is a "show"');
 
     resetEvents();
     popover.hidePopover();
     popover.showPopover(); // Immediate re-show
-    await waitForTick();
+    await waitForRender();
     assert_true(popover.matches(':popover-open'));
     assertOnly('coalescedShow','Single coalesced event should have been fired, which is a "show"');
 
     resetEvents();
     popover.hidePopover();
-    await waitForTick();
+    await waitForRender();
     assertOnly('singleHide','Single event should have been fired, which is a "hide"');
     assert_false(popover.matches(':popover-open'));
 
     resetEvents();
     popover.showPopover();
     popover.hidePopover(); // Immediate re-hide
-    await waitForTick();
+    await waitForRender();
     assertOnly('coalescedHide','Single coalesced event should have been fired, which is a "hide"');
     assert_false(popover.matches(':popover-open'));
   }, 'The "toggle" event is coalesced');