public Properties chain(Properties chained) {
        this.chained = chained;
        return chained;
    }
Sets the properties chained to this.

@param chained the properties to chain to this, or null to make this the last in the chain
@return the given chained object to allow setting up a chain by dotting in one statement
container-core/src/main/java/com/yahoo/processing/request/Properties.java