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
*/
	public FindReferencesInWorkingSetAction(JavaEditor editor, IWorkingSet[] workingSets) {
		super(editor);
		fWorkingSets= workingSets;
	}
	
	void init() {
		setText(SearchMessages.Search_FindReferencesInWorkingSetAction_label); 
		setToolTipText(SearchMessages.Search_FindReferencesInWorkingSetAction_tooltip); 
		setImageDescriptor(JavaPluginImages.DESC_OBJS_SEARCH_REF);
		PlatformUI.getWorkbench().getHelpSystem().setHelp(this, IJavaHelpContextIds.FIND_REFERENCES_IN_WORKING_SET_ACTION);
	}
	protected JavaSearchQuery createJob(IJavaElement element) throws JavaModelException {
		IWorkingSet[] workingSets= fWorkingSets;
		if (fWorkingSets == null) {
			workingSets= JavaSearchScopeFactory.getInstance().queryWorkingSets();
			if (workingSets == null)
				return null;
		}
		SearchUtil.updateLRUWorkingSets(workingSets);
		return new JavaSearchQuery(new ElementQuerySpecification(element, getLimitTo(), getScope(workingSets), getScopeDescription(workingSets)));
	}
	private IJavaSearchScope getScope(IWorkingSet[] workingSets) {
		return JavaSearchScopeFactory.getInstance().createJavaSearchScope(workingSets, JavaSearchPage.getSearchJRE());
	}
	private String getScopeDescription(IWorkingSet[] workingSets) {
		return Messages.format(SearchMessages.WorkingSetScope, new String[] {SearchUtil.toString(workingSets)}); 
	}
}