@CanIgnoreReturnValue
    public ChainingThemeResolver addResolver(final ThemeResolver r) {
        chain.add(r);
        return this;
    }
Add resolver to the chain.

@param r the resolver
@return the chaining theme resolver
support/cas-server-support-themes-core/src/main/java/org/apereo/cas/services/web/ChainingThemeResolver.java