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

Source/web/WebInputEventConversion.cpp

 /*
  * Copyright (C) 2009 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 41 matching lines @@
 
 namespace WebKit {
 
 static const double millisPerSecond = 1000.0;
 
 static float widgetInputEventsScaleFactor(const Widget* widget)
 {
     if (!widget)
         return 1;
 
-    ScrollView* rootView = widget->root();
+    ScrollView* rootView =  toScrollView(widget->root());
     if (!rootView)
         return 1;
 
     return rootView->inputEventsScaleFactor();
 }
 
 // MakePlatformMouseEvent -----------------------------------------------------
 
 PlatformMouseEventBuilder::PlatformMouseEventBuilder(Widget* widget, const WebMouseEvent& e)
 {
@@ skipping 358 matching lines @@
 static IntPoint convertAbsoluteLocationForRenderObject(const LayoutPoint& location, const WebCore::RenderObject& renderObject)
 {
     return roundedIntPoint(renderObject.absoluteToLocal(location, UseTransforms));
 }
 
 static void updateWebMouseEventFromWebCoreMouseEvent(const MouseRelatedEvent& event, const Widget& widget, const WebCore::RenderObject& renderObject, WebMouseEvent& webEvent)
 {
     webEvent.timeStampSeconds = event.timeStamp() / millisPerSecond;
     webEvent.modifiers = getWebInputModifiers(event);
 
-    ScrollView* view = widget.parent();
+    ScrollView* view =  toScrollView(widget.parent());
     IntPoint windowPoint = IntPoint(event.absoluteLocation().x(), event.absoluteLocation().y());
     if (view)
         windowPoint = view->contentsToWindow(windowPoint);
     webEvent.globalX = event.screenX();
     webEvent.globalY = event.screenY();
     webEvent.windowX = windowPoint.x();
     webEvent.windowY = windowPoint.y();
     IntPoint localPoint = convertAbsoluteLocationForRenderObject(event.absoluteLocation(), renderObject);
     webEvent.x = localPoint.x();
     webEvent.y = localPoint.y();
@@ skipping 291 matching lines @@
     modifiers = getWebInputModifiers(event);
 
     globalX = event.screenX();
     globalY = event.screenY();
     IntPoint localPoint = convertAbsoluteLocationForRenderObject(event.absoluteLocation(), *renderObject);
     x = localPoint.x();
     y = localPoint.y();
 }
 
 } // namespace WebKit