Gathers additional named properties of the instance and adds their current values
to the passed state object.
@param {String/String[]} propNames The name (or array of names) of the property to save.
@param {Object} state The state object in to which to save the property values.
@return {Object} state
function (propNames, state) {
        var me = this,
            i, n;

        if (typeof propNames == 'string') {
            me.savePropToState(propNames, state);
        } else {
            for (i = 0, n = propNames.length; i < n; ++i) {
                me.savePropToState(propNames[i], state);
            }
        }

        return state;
    }