Introduce DEFINE_RENDER_OBJECT_TYPE_CASTS to replace manual toRenderFoo, and use it

Source/core/rendering/RenderNamedFlowThread.h

Index: Source/core/rendering/RenderNamedFlowThread.h
diff --git a/Source/core/rendering/RenderNamedFlowThread.h b/Source/core/rendering/RenderNamedFlowThread.h
index dfe453391b5e5714506cc24d01653f329730cd47..6528c1106c56548933752e78985b550fae9ee8a8 100644
--- a/Source/core/rendering/RenderNamedFlowThread.h
+++ b/Source/core/rendering/RenderNamedFlowThread.h
@@ -136,20 +136,7 @@ private:
     Timer<RenderNamedFlowThread> m_regionOversetChangeEventTimer;
 };
 
-inline RenderNamedFlowThread* toRenderNamedFlowThread(RenderObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderNamedFlowThread());
-    return static_cast<RenderNamedFlowThread*>(object);
-}
-
-inline const RenderNamedFlowThread* toRenderNamedFlowThread(const RenderObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderNamedFlowThread());
-    return static_cast<const RenderNamedFlowThread*>(object);
-}
-
-// This will catch anyone doing an unnecessary cast.
-void toRenderNamedFlowThread(const RenderNamedFlowThread*);
+DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderNamedFlowThread, isRenderNamedFlowThread());
 
 } // namespace WebCore