Introduce DEFINE_RENDER_OBJECT_TYPE_CASTS to replace manual toRenderFoo, and use it

Source/core/rendering/RenderBR.h

Index: Source/core/rendering/RenderBR.h
diff --git a/Source/core/rendering/RenderBR.h b/Source/core/rendering/RenderBR.h
index a5ad8ff1f80b6840b557e0ed9e25d73cad33c774..62d1a53479eb012542ec5f70a2186d1317e3fb9b 100644
--- a/Source/core/rendering/RenderBR.h
+++ b/Source/core/rendering/RenderBR.h
@@ -60,21 +60,7 @@ private:
     mutable int m_lineHeight;
 };
 
-
-inline RenderBR* toRenderBR(RenderObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isBR());
-    return static_cast<RenderBR*>(object);
-}
-
-inline const RenderBR* toRenderBR(const RenderObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isBR());
-    return static_cast<const RenderBR*>(object);
-}
-
-// This will catch anyone doing an unnecessary cast.
-void toRenderBR(const RenderBR*);
+DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderBR, isBR());
 
 } // namespace WebCore