Smaller vtbls in RenderObject

Source/core/rendering/RenderScrollbarPart.h

 /*
  * Copyright (C) 2008 Apple 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 33 matching lines @@
     virtual LayerType layerTypeRequired() const override { return NoLayer; }
 
     virtual void layout() override;
 
     // Scrollbar parts needs to be rendered at device pixel boundaries.
     virtual LayoutUnit marginTop() const override { ASSERT(isIntegerValue(m_marginBox.top())); return m_marginBox.top(); }
     virtual LayoutUnit marginBottom() const override { ASSERT(isIntegerValue(m_marginBox.bottom())); return m_marginBox.bottom(); }
     virtual LayoutUnit marginLeft() const override { ASSERT(isIntegerValue(m_marginBox.left())); return m_marginBox.left(); }
     virtual LayoutUnit marginRight() const override { ASSERT(isIntegerValue(m_marginBox.right())); return m_marginBox.right(); }
 
-    virtual bool isRenderScrollbarPart() const override { return true; }
+    virtual bool isOfType(RenderObjectType type) const override { return type == RenderObjectRenderScrollbarPart || RenderBlock::isOfType(type); }
     RenderObject* rendererOwningScrollbar() const;
 
 protected:
     virtual void styleWillChange(StyleDifference, const RenderStyle& newStyle) override;
     virtual void styleDidChange(StyleDifference, const RenderStyle* oldStyle) override;
     virtual void imageChanged(WrappedImagePtr, const IntRect* = 0) override;
 
 private:
     RenderScrollbarPart(RenderScrollbar*, ScrollbarPart);
 
@@ skipping 20 matching lines @@
 
     RenderScrollbar* m_scrollbar;
     ScrollbarPart m_part;
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderScrollbarPart, isRenderScrollbarPart());
 
 } // namespace blink
 
 #endif // RenderScrollbarPart_h