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

Source/core/platform/ScrollView.h

 /*
  * Copyright (C) 2004, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Holger Hans Peter Freyther
  *
  * 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
@@ skipping 179 matching lines @@
     // we know that we are either not in a window right now or if that window is not visible.
     bool isOffscreen() const;
 
     // These functions are used to enable scrollbars to avoid window resizer controls that overlap the scroll view. This happens on Mac
     // for example.
     virtual IntRect windowResizerRect() const { return IntRect(); }
     bool containsScrollbarsAvoidingResizer() const;
     void adjustScrollbarsAvoidingResizerCount(int overlapDelta);
     void windowResizerRectChanged();
 
-    virtual void setParent(ScrollView*); // Overridden to update the overlapping scrollbar count.
+    virtual void setParent(Widget*) OVERRIDE; // Overridden to update the overlapping scrollbar count.
 
     // Called when our frame rect changes (or the rect/scroll position of an ancestor changes).
     virtual void frameRectsChanged();
 
     // Widget override to update our scrollbars and notify our contents of the resize.
     virtual void setFrameRect(const IntRect&);
 
     // Widget override to notify our contents of a cliprect change.
     virtual void clipRectChanged() OVERRIDE;
 
     // For platforms that need to hit test scrollbars from within the engine's event handlers (like Win32).
     Scrollbar* scrollbarAtPoint(const IntPoint& windowPoint);
 
-    IntPoint convertChildToSelf(const Widget* child, const IntPoint& point) const
+    virtual IntPoint convertChildToSelf(const Widget* child, const IntPoint& point) const
     {
         IntPoint newPoint = point;
         if (!isScrollViewScrollbar(child))
             newPoint = point - scrollOffset();
         newPoint.moveBy(child->location());
         return newPoint;
     }
 
-    IntPoint convertSelfToChild(const Widget* child, const IntPoint& point) const
+    virtual IntPoint convertSelfToChild(const Widget* child, const IntPoint& point) const
     {
         IntPoint newPoint = point;
         if (!isScrollViewScrollbar(child))
             newPoint = point + scrollOffset();
         newPoint.moveBy(-child->location());
         return newPoint;
     }
 
+    // A means to access the AX cache when this object can get a pointer to it.
+    virtual AXObjectCache* axObjectCache() const { return 0; }
+
     // Widget override. Handles painting of the contents of the view as well as the scrollbars.
     virtual void paint(GraphicsContext*, const IntRect&);
     void paintScrollbars(GraphicsContext*, const IntRect&);
 
     // Widget overrides to ensure that our children's visibility status is kept up to date when we get shown and hidden.
     virtual void show();
     virtual void hide();
     virtual void setParentVisible(bool);
 
     // Pan scrolling.
@@ skipping 107 matching lines @@
     ASSERT(!widget || widget->isScrollView());
     return static_cast<const ScrollView*>(widget);
 }
 
 // This will catch anyone doing an unnecessary cast.
 void toScrollView(const ScrollView*);
 
 } // namespace WebCore
 
 #endif // ScrollView_h