8311805: Clean up ScrollPane: drop redundant initialiser, mark scroller final

Reviewed-by: azvegint, serb, prr

Author: aivanov-jdk

src/java.desktop/share/classes/java/awt/ScrollPane.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2023, 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
@@ -507,7 +507,6 @@ public void layout() {
         Component c = getComponent(0);
         Point p = getScrollPosition();
         Dimension cs = calculateChildSize();
-        Dimension vs = getViewportSize();
 
         c.reshape(- p.x, - p.y, cs.width, cs.height);
         ScrollPanePeer peer = (ScrollPanePeer)this.peer;
@@ -518,7 +517,7 @@ public void layout() {
         // update adjustables... the viewport size may have changed
         // with the scrollbars coming or going so the viewport size
         // is updated before the adjustables.
-        vs = getViewportSize();
+        Dimension vs = getViewportSize();
         hAdjustable.setSpan(0, cs.width, vs.width);
         vAdjustable.setSpan(0, cs.height, vs.height);
     }
@@ -776,7 +775,7 @@ public void adjustmentValueChanged(AdjustmentEvent e) {
             }
         }
 
-        private ScrollPane scroller;
+        private final ScrollPane scroller;
     }