Remove Widget's dependency upon its own inheritor aka ScrollView. This was nasty from an OO design…

Source/core/platform/ScrollView.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 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 627 matching lines @@
 bool ScrollView::containsScrollbarsAvoidingResizer() const
 {
     return !m_scrollbarsAvoidingResizer;
 }
 
 void ScrollView::adjustScrollbarsAvoidingResizerCount(int overlapDelta)
 {
     int oldCount = m_scrollbarsAvoidingResizer;
     m_scrollbarsAvoidingResizer += overlapDelta;
     if (parent())
-        parent()->adjustScrollbarsAvoidingResizerCount(overlapDelta);
+        toScrollView(parent())->adjustScrollbarsAvoidingResizerCount(overlapDelta);
     else if (!scrollbarsSuppressed()) {
         // If we went from n to 0 or from 0 to n and we're the outermost view,
         // we need to invalidate the windowResizerRect(), since it will now need to paint
         // differently.
         if ((oldCount > 0 && m_scrollbarsAvoidingResizer == 0) ||
             (oldCount == 0 && m_scrollbarsAvoidingResizer > 0))
             invalidateRect(windowResizerRect());
     }
 }
 
-void ScrollView::setParent(ScrollView* parentView)
+void ScrollView::setParent(Widget* parentView)
 {
     if (parentView == parent())
         return;
 
     if (m_scrollbarsAvoidingResizer && parent())
-        parent()->adjustScrollbarsAvoidingResizerCount(-m_scrollbarsAvoidingResizer);
+        toScrollView(parent())->adjustScrollbarsAvoidingResizerCount(-m_scrollbarsAvoidingResizer);
 
     Widget::setParent(parentView);
 
     if (m_scrollbarsAvoidingResizer && parent())
-        parent()->adjustScrollbarsAvoidingResizerCount(m_scrollbarsAvoidingResizer);
+        toScrollView(parent())->adjustScrollbarsAvoidingResizerCount(m_scrollbarsAvoidingResizer);
 }
 
 void ScrollView::setScrollbarsSuppressed(bool suppressed, bool repaintOnUnsuppress)
 {
     if (suppressed == m_scrollbarsSuppressed)
         return;
 
     m_scrollbarsSuppressed = suppressed;
 
     if (repaintOnUnsuppress && !suppressed) {
@@ skipping 178 matching lines @@
     if (layerForScrollCorner())
         return;
     paintScrollCorner(context, scrollCornerRect());
 }
 
 void ScrollView::paintPanScrollIcon(GraphicsContext* context)
 {
     static Image* panScrollIcon = Image::loadPlatformResource("panIcon").leakRef();
     IntPoint iconGCPoint = m_panScrollIconPoint;
     if (parent())
-        iconGCPoint = parent()->windowToContents(iconGCPoint);
+        iconGCPoint = toScrollView(parent())->windowToContents(iconGCPoint);
     context->drawImage(panScrollIcon, iconGCPoint);
 }
 
 void ScrollView::paint(GraphicsContext* context, const IntRect& rect)
 {
     if (context->paintingDisabled() && !context->updatingControlTints())
         return;
 
     notifyPageThatContentAreaWillPaint();
 
@@ skipping 277 matching lines @@
 int ScrollView::pageStep(ScrollbarOrientation orientation) const
 {
     int length = (orientation == HorizontalScrollbar) ? visibleWidth() : visibleHeight();
     int minPageStep = static_cast<float>(length) * minFractionToStepWhenPaging();
     int pageStep = std::max(minPageStep, length - maxOverlapBetweenPages());
 
     return std::max(pageStep, 1);
 }
 
 } // namespace WebCore