torage.  The getter returns the value in the local storage,
       * and the setter calls `_setProperty`, which updates the local storage
       * for the property and enqueues a `_propertiesChanged` callback.
       *
       * This method may be called on a prototype or an instance.  Calling
       * this method may overwrite a property value that already exists on
       * the prototype/instance by creating the accessor.  When calling on
       * a prototype, any overwritten values are saved in `__dataPro