in src/main/java/org/apache/sling/jcr/jackrabbit/base/security/DelegatingPrincipalProviderRegistry.java [47:53]
public PrincipalProvider getProvider(String name) {
PrincipalProvider p = defaultRegistry.getProvider(name);
if (p == null) {
p = osgiRegistry.getProvider(name);
}
return p;
}