8353620: Make some systems tests robust for Ubuntu 24.04

Reviewed-by: kcr

Author: jayathirthrao

tests/system/src/test/java/test/robot/javafx/scene/MenuDoubleShortcutTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2024, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -115,6 +115,7 @@ void nonMacMenuBarComesBeforeScene() {
 
     @Test
     void acceleratorOnlyInMenuBar() {
+        Util.sleep(delayMilliseconds);
         testApp.testKey(menuBarOnlyKeyCode);
         Util.sleep(delayMilliseconds);
         TestResult result = testApp.testResult();

tests/system/src/test/java/test/robot/javafx/stage/KeyEventClosesStageTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -66,6 +66,7 @@ public class KeyEventClosesStageTest {
     @BeforeAll
     public static void initFX() throws Exception {
         Util.launch(startupLatch, TestApp.class);
+        Util.sleep(200);
 
         // When run from the command line Windows does not want to
         // activate the window.

tests/system/src/test/java/test/robot/javafx/web/TextSelectionTest.java

@@ -71,6 +71,7 @@ public void beforeEach() {
     @Timeout(value=20)
     public void testTextSelection() {
 
+        Util.sleep(200);
         int x = (int)(scene.getWindow().getX() + scene.getX() + 22);
         int y = (int)(scene.getWindow().getY() + scene.getY() + 15);