/**
  * Gets the session tracking modes that are supported by default for this <tt>ServletContext</tt>.
  *
  * @return set of the session tracking modes supported by default for this <tt>ServletContext</tt>
  */
 @Override
 @SuppressWarnings("unchecked") // doPrivileged() returns the correct type
 public Set<SessionTrackingMode> getDefaultSessionTrackingModes() {
   if (SecurityUtil.isPackageProtectionEnabled()) {
     return (Set<SessionTrackingMode>) doPrivileged("getDefaultSessionTrackingModes", null);
   } else {
     return context.getDefaultSessionTrackingModes();
   }
 }