[serialize] Make putting breakpoint on out-of-memory easier

src/hb-serialize.hh

@@ -323,6 +323,9 @@ struct hb_serialize_context_t
     return ret;
   }
 
+  void
+  err_ran_out_of_room () { this->ran_out_of_room = true; }
+
   template <typename Type>
   Type *allocate_size (unsigned int size)
   {
@@ -330,7 +333,7 @@ struct hb_serialize_context_t
 
     if (this->tail - this->head < ptrdiff_t (size))
     {
-      this->ran_out_of_room = true;
+      err_ran_out_of_room ();
       this->successful = false;
       return nullptr;
     }