Introduce DEFINE_RENDER_OBJECT_TYPE_CASTS to replace manual toRenderFoo, and use it

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 60 matching lines @@
     void layoutHorizontalPart();
     void layoutVerticalPart();
 
     void computeScrollbarWidth();
     void computeScrollbarHeight();
 
     RenderScrollbar* m_scrollbar;
     ScrollbarPart m_part;
 };
 
-inline RenderScrollbarPart* toRenderScrollbarPart(RenderObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderScrollbarPart());
-    return static_cast<RenderScrollbarPart*>(object);
-}
-
-inline const RenderScrollbarPart* toRenderScrollbarPart(const RenderObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderScrollbarPart());
-    return static_cast<const RenderScrollbarPart*>(object);
-}
-
-// This will catch anyone doing an unnecessary cast.
-void toRenderScrollbarPart(const RenderScrollbarPart*);
+DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderScrollbarPart, isRenderScrollbarPart());
 
 } // namespace WebCore
 
 #endif // RenderScrollbarPart_h