Remove concept of child Widgets.

sky/engine/core/rendering/RenderLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 770 matching lines @@
     return IntSize();
 }
 
 PassRefPtr<Scrollbar> RenderLayerScrollableArea::createScrollbar(ScrollbarOrientation orientation)
 {
     RefPtr<Scrollbar> widget = Scrollbar::create(this, orientation);
     if (orientation == HorizontalScrollbar)
         didAddScrollbar(widget.get(), HorizontalScrollbar);
     else
         didAddScrollbar(widget.get(), VerticalScrollbar);
-    box().document().view()->addChild(widget.get());
     return widget.release();
 }
 
 void RenderLayerScrollableArea::destroyScrollbar(ScrollbarOrientation orientation)
 {
     RefPtr<Scrollbar>& scrollbar = orientation == HorizontalScrollbar ? m_hBar : m_vBar;
     if (!scrollbar)
         return;
 
     if (!scrollbar->isCustomScrollbar())
         willRemoveScrollbar(scrollbar.get(), orientation);
 
-    scrollbar->removeFromParent();
     scrollbar->disconnectFromScrollableArea();
     scrollbar = nullptr;
 }
 
 void RenderLayerScrollableArea::setHasHorizontalScrollbar(bool hasScrollbar)
 {
     if (hasScrollbar == hasHorizontalScrollbar())
         return;
 
     if (hasScrollbar) {
@@ skipping 505 matching lines @@
 void RenderLayerScrollableArea::setTopmostScrollChild(RenderLayer* scrollChild)
 {
     // We only want to track the topmost scroll child for scrollable areas with
     // overlay scrollbars.
     if (!hasOverlayScrollbars())
         return;
     m_nextTopmostScrollChild = scrollChild;
 }
 
 } // namespace blink