Bug 91409 Project Open/Close items are disabled when Package Explorer active
Project Open/Close option in the Project menu is disabled in Plugin prespective.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/workingsets/OpenCloseWorkingSetAction.java
protected abstract String getErrorTitle();
	protected abstract String getErrorMessage();
	
	private List getProjects(IStructuredSelection selection) {
		List result= new ArrayList();
		List elements= selection.toList();
		for (Iterator iter= elements.iterator(); iter.hasNext();) {
			Object element= iter.next();
			if (!(element instanceof IWorkingSet))
				return null;
			List projects= getProjects((IWorkingSet)element);
			if (projects == null)
				return null;
			result.addAll(projects);
		}
		return result;
	}
	private List getProjects(IWorkingSet set) {
		List result= new ArrayList();
		IAdaptable[] elements= set.getElements();
		for (int i= 0; i < elements.length; i++) {
			Object element= elements[i];
			IProject project= null;
			if (element instanceof IProject) {
				project= (IProject)element;
			} else if (element instanceof IJavaProject) {
				project= ((IJavaProject)element).getProject();
			}
			if (project == null || !validate(project))
				return null;