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

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 3180 matching lines @@
     IntPoint point = viewPoint;
 
     // Convert from FrameView coords into page ("absolute") coordinates.
     point += IntSize(scrollX(), scrollY());
 
     return roundedIntPoint(renderer->absoluteToLocal(point, UseTransforms));
 }
 
 IntRect FrameView::convertToContainingView(const IntRect& localRect) const
 {
-    if (const ScrollView* parentScrollView = parent()) {
+    if (const ScrollView* parentScrollView = toScrollView(parent())) {
         if (parentScrollView->isFrameView()) {
             const FrameView* parentView = toFrameView(parentScrollView);
             // Get our renderer in the parent view
             RenderPart* renderer = m_frame->ownerRenderer();
             if (!renderer)
                 return localRect;
 
             IntRect rect(localRect);
             // Add borders and padding??
             rect.move(renderer->borderLeft() + renderer->paddingLeft(),
                 renderer->borderTop() + renderer->paddingTop());
             return parentView->convertFromRenderer(renderer, rect);
         }
 
         return Widget::convertToContainingView(localRect);
     }
 
     return localRect;
 }
 
 IntRect FrameView::convertFromContainingView(const IntRect& parentRect) const
 {
-    if (const ScrollView* parentScrollView = parent()) {
+    if (const ScrollView* parentScrollView = toScrollView(parent())) {
         if (parentScrollView->isFrameView()) {
             const FrameView* parentView = toFrameView(parentScrollView);
 
             // Get our renderer in the parent view
             RenderPart* renderer = m_frame->ownerRenderer();
             if (!renderer)
                 return parentRect;
 
             IntRect rect = parentView->convertToRenderer(renderer, parentRect);
             // Subtract borders and padding
             rect.move(-renderer->borderLeft() - renderer->paddingLeft(),
                       -renderer->borderTop() - renderer->paddingTop());
             return rect;
         }
 
         return Widget::convertFromContainingView(parentRect);
     }
 
     return parentRect;
 }
 
 IntPoint FrameView::convertToContainingView(const IntPoint& localPoint) const
 {
-    if (const ScrollView* parentScrollView = parent()) {
+    if (const ScrollView* parentScrollView = toScrollView(parent())) {
         if (parentScrollView->isFrameView()) {
             const FrameView* parentView = toFrameView(parentScrollView);
 
             // Get our renderer in the parent view
             RenderPart* renderer = m_frame->ownerRenderer();
             if (!renderer)
                 return localPoint;
 
             IntPoint point(localPoint);
 
             // Add borders and padding
             point.move(renderer->borderLeft() + renderer->paddingLeft(),
                        renderer->borderTop() + renderer->paddingTop());
             return parentView->convertFromRenderer(renderer, point);
         }
 
         return Widget::convertToContainingView(localPoint);
     }
 
     return localPoint;
 }
 
 IntPoint FrameView::convertFromContainingView(const IntPoint& parentPoint) const
 {
-    if (const ScrollView* parentScrollView = parent()) {
+    if (const ScrollView* parentScrollView = toScrollView(parent())) {
         if (parentScrollView->isFrameView()) {
             const FrameView* parentView = toFrameView(parentScrollView);
 
             // Get our renderer in the parent view
             RenderPart* renderer = m_frame->ownerRenderer();
             if (!renderer)
                 return parentPoint;
 
             IntPoint point = parentView->convertToRenderer(renderer, parentPoint);
             // Subtract borders and padding
@@ skipping 174 matching lines @@
 void FrameView::setLayoutSizeInternal(const IntSize& size)
 {
     if (m_layoutSize == size)
         return;
 
     m_layoutSize = size;
     contentsResized();
 }
 
 } // namespace WebCore