message: RefCounted: make copy constructor arg const
diff: @@ -48,7 +48,7 @@ namespace backend {
  Reference();
  }
  - Ref(Ref<T>& other): pointee(other.pointee) {
  + Ref(const Ref<T>& other): pointee(other.pointee) {
  Reference();
  }
  Ref<T>& operator=(const Ref<T>& other) {
  