[Fix] Revert removed setTimeout on EuiInputPopover scroll listener

packages/eui/changelogs/upcoming/7760.md

@@ -0,0 +1,4 @@
+**Bug fixes**
+
+- Restored a removed `setTimeout` in `EuiInputPopover` to reduce flaky Cypress failures
+

packages/eui/src/components/popover/input_popover.tsx

@@ -190,15 +190,20 @@ export const EuiInputPopover: FunctionComponent<EuiInputPopoverProps> = ({
         closePopover();
       };
 
-      window.addEventListener('scroll', closePopoverOnScroll, {
-        passive: true, // for better performance as we won't call preventDefault
-        capture: true, // scroll events don't bubble, they must be captured instead
-      });
+      // Kibana Cypress tests trigger a scroll event in many common situations when the options list div is appended
+      // to the DOM; in testing it was always within 100ms, but setting a timeout here for 500ms to be safe
+      const timeoutId = setTimeout(() => {
+        window.addEventListener('scroll', closePopoverOnScroll, {
+          passive: true, // for better performance as we won't call preventDefault
+          capture: true, // scroll events don't bubble, they must be captured instead
+        });
+      }, 500);
 
       return () => {
         window.removeEventListener('scroll', closePopoverOnScroll, {
           capture: true,
         });
+        clearTimeout(timeoutId);
       };
     }
   }, [closeOnScroll, closePopover, panelEl, inputEl]);