Fixed Inconsistent behaviour of custom-scrollbar

Source/core/rendering/RenderScrollbar.cpp

 /*
  * Copyright (C) 2008, 2009 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 105 matching lines @@
 {
     Scrollbar::setParent(parent);
     if (!parent) {
         // Destroy all of the scrollbar's RenderBoxes.
         updateScrollbarParts(true);
     }
 }
 
 void RenderScrollbar::setEnabled(bool e)
 {
-    bool wasEnabled = enabled();
     Scrollbar::setEnabled(e);
-    if (wasEnabled != e)
-        updateScrollbarParts();
+    updateScrollbarParts();
 }
 
 void RenderScrollbar::styleChanged()
 {
     updateScrollbarParts();
 }
 
 void RenderScrollbar::setHoveredPart(ScrollbarPart part)
 {
     if (part == m_hoveredPart)
@@ skipping 218 matching lines @@
 int RenderScrollbar::minimumThumbLength()
 {
     RenderScrollbarPart* partRenderer = m_parts.get(ThumbPart);
     if (!partRenderer)
         return 0;
     partRenderer->layout();
     return orientation() == HorizontalScrollbar ? partRenderer->width() : partRenderer->height();
 }
 
 }