code: public synchronized void setWorkbenchEntry(final WorkbenchEntry workbenchEntry) {
  		assert ! acquired : this;
  		this.workbenchEntry = workbenchEntry;
  		if (! isEmpty()) workbenchEntry.add(this, frontier.workbench);
  	}
docs: Sets the workbench entry and put this visit state in its entry if it is nonempty.
  
  <ul>
  <li>Preconditions: not {{@link #acquired}}.
  </ul>