--- a/dom/animation/AnimValuesStyleRule.h
+++ b/dom/animation/AnimValuesStyleRule.h
@@ -54,23 +54,16 @@ public:
     return &p->mValue;
   }
 
   struct PropertyValuePair {
     nsCSSProperty mProperty;
     StyleAnimationValue mValue;
   };
 
-  void AddPropertiesToSet(nsCSSPropertySet& aSet) const
-  {
-    for (const PropertyValuePair& cv : mPropertyValuePairs) {
-      aSet.AddProperty(cv.mProperty);
-    }
-  }
-
 private:
   ~AnimValuesStyleRule() {}
 
   InfallibleTArray<PropertyValuePair> mPropertyValuePairs;
   uint32_t mStyleBits;
 };
 
 } // namespace mozilla