Introduce DEFINE_RENDER_OBJECT_TYPE_CASTS to replace manual toRenderFoo, and use it

Source/core/rendering/RenderMultiColumnBlock.h

Index: Source/core/rendering/RenderMultiColumnBlock.h
diff --git a/Source/core/rendering/RenderMultiColumnBlock.h b/Source/core/rendering/RenderMultiColumnBlock.h
index 25e3168eefb851ca63476d1c0386a57c965ab048..ac92d2f9ff927dfbed292ddf7d0967a4fe238ed4 100644
--- a/Source/core/rendering/RenderMultiColumnBlock.h
+++ b/Source/core/rendering/RenderMultiColumnBlock.h
@@ -75,20 +75,7 @@ private:
     bool m_inBalancingPass; // Set when relayouting for column balancing.
 };
 
-inline RenderMultiColumnBlock* toRenderMultiColumnBlock(RenderObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderMultiColumnBlock());
-    return static_cast<RenderMultiColumnBlock*>(object);
-}
-
-inline const RenderMultiColumnBlock* toRenderMultiColumnBlock(const RenderObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderMultiColumnBlock());
-    return static_cast<const RenderMultiColumnBlock*>(object);
-}
-
-// This will catch anyone doing an unnecessary cast.
-void toRenderMultiColumnBlock(const RenderMultiColumnBlock*);
+DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderMultiColumnBlock, isRenderMultiColumnBlock());
 
 } // namespace WebCore