Bug 68011 [java search] "Search the JRE System Libraries" looks like a local preference but behaves as a global one... [search]
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/actions/FindReferencesInWorkingSetAction.java
* be prompted to select the working sets.
	 * 
	 * @param site the site providing context information for this action
	 */
	public FindReferencesInWorkingSetAction(IWorkbenchSite site) {
		this(site, null);
	}
	/**
	 * Creates a new <code>FindReferencesInWorkingSetAction</code>. The action 
	 * requires that the selection provided by the site's selection provider is of type 
	 * <code>org.eclipse.jface.viewers.IStructuredSelection</code>.
	 * 
	 * @param site			the site providing context information for this action
	 * @param workingSets	the working sets to be used in the search
	 */
	public FindReferencesInWorkingSetAction(IWorkbenchSite site, IWorkingSet[] workingSets) {
		super(site);
		fWorkingSets= workingSets;
	}
	/**
	 * Note: This constructor is for internal use only. Clients should not call this constructor.
	 * @param editor the Java editor
	 */
	public FindReferencesInWorkingSetAction(JavaEditor editor) {
		this(editor, null);
	}
	/**
	 * Note: This constructor is for internal use only. Clients should not call this constructor.
	 * @param editor the Java editor
	 * @param workingSets the working sets to be used in the search