Introduce DEFINE_RENDER_OBJECT_TYPE_CASTS to replace manual toRenderFoo, and use it

Source/core/rendering/RenderCounter.h

Index: Source/core/rendering/RenderCounter.h
diff --git a/Source/core/rendering/RenderCounter.h b/Source/core/rendering/RenderCounter.h
index 3fa3fdd350c345f2cb6bfb80c949c5772fc73568..61cb9ffb3a01083a251f7f12a101e138cddcc2af 100644
--- a/Source/core/rendering/RenderCounter.h
+++ b/Source/core/rendering/RenderCounter.h
@@ -60,14 +60,7 @@ private:
     friend class CounterNode;
 };
 
-inline RenderCounter* toRenderCounter(RenderObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isCounter());
-    return static_cast<RenderCounter*>(object);
-}
-
-// This will catch anyone doing an unnecessary cast.
-void toRenderCounter(const RenderCounter*);
+DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderCounter, isCounter());
 
 } // namespace WebCore