code: public CmsWaitHandle addFormatterCacheWaitHandle(boolean online) {
  
          CmsWaitHandle handle = new CmsWaitHandle(true); // single use wait handle
          CmsFormatterConfigurationCache cache = online ? m_onlineFormatterCache : m_offlineFormatterCache;
          cache.addWaitHandle(handle);
          return handle;
  
      }
docs: Adds a wait handle for the next cache update to a formatter configuration.<p>
  
  @param online true if we want to add a wait handle to the online cache, else the offline cache
  @return the wait handle that has been added