Fix regression introduced with r159483. The RenderScrollbar's parent class had the signature of a …

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 69 matching lines @@
 
 RenderBox* RenderScrollbar::owningRenderer() const
 {
     if (m_owningFrame) {
         RenderBox* currentRenderer = m_owningFrame->ownerRenderer();
         return currentRenderer;
     }
     return m_owner && m_owner->renderer() ? m_owner->renderer()->enclosingBox() : 0;
 }
 
-void RenderScrollbar::setParent(ScrollView* parent)
+void RenderScrollbar::setParent(Widget* parent)
 {
     Scrollbar::setParent(parent);
     if (!parent) {
         // Destroy all of the scrollbar's RenderBoxes.
         updateScrollbarParts(true);
     }
 }
 
 void RenderScrollbar::setEnabled(bool e)
 {
@@ skipping 249 matching lines @@
 int RenderScrollbar::minimumThumbLength()
 {
     RenderScrollbarPart* partRenderer = m_parts.get(ThumbPart);
     if (!partRenderer)
         return 0;
     partRenderer->layout();
     return orientation() == HorizontalScrollbar ? partRenderer->width() : partRenderer->height();
 }
 
 }