ance-specific properties that change on the instance should be
     * forwarded out to the host, if necessary.
     *
     *     _notifyInstancePropV2: function(inst, prop, value)
     *
     * In order to determine which properties are instance-specific and require
     * custom notification via `_notifyInstanceProp`, define an `_instanceProps`
     * object containing keys for each instance prop, for example:
     *
     *     _instanceProps: {
     *       item: true,
     *       index: true
     *     