Remove concept of child Widgets.

sky/engine/platform/scroll/Scrollbar.h

 /*
  * Copyright (C) 2004, 2006 Apple Computer, 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 40 matching lines @@
     int x() const { return Widget::x(); }
     int y() const { return Widget::y(); }
     int width() const { return Widget::width(); }
     int height() const { return Widget::height(); }
     IntSize size() const { return Widget::size(); }
     IntPoint location() const { return Widget::location(); }
 
     Widget* parent() const { return Widget::parent(); }
     Widget* root() const { return Widget::root(); }
 
-    void removeFromParent();
-
     void setFrameRect(const IntRect& r) { Widget::setFrameRect(r); }
     IntRect frameRect() const { return Widget::frameRect(); }
 
     void invalidate() { Widget::invalidate(); }
     void invalidateRect(const IntRect&);
 
     ScrollbarOverlayStyle scrollbarOverlayStyle() const;
     void getTickmarks(Vector<IntRect>&) const;
     bool isScrollableAreaActive() const;
     bool isScrollViewScrollbar() const;
@@ skipping 150 matching lines @@
     virtual bool isScrollbar() const override { return true; }
 
     float scrollableAreaCurrentPos() const;
 };
 
 DEFINE_TYPE_CASTS(Scrollbar, Widget, widget, widget->isScrollbar(), widget.isScrollbar());
 
 } // namespace blink
 
 #endif // Scrollbar_h