Bug 81877 Package explorer forgets active working set [package explorer]
3.1 M4 1. open pkg explorer. 2. select a working set, pkg explorer updates and filters out projects. 3. close pkg explorer. 4. open package explorer again and the working set is no longer applied. This used to work.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
return element2;
    }
    private boolean revealAndVerify(Object element) {
    	if (element == null)
    		return false;
    	selectReveal(new StructuredSelection(element));
    	return ! getSite().getSelectionProvider().getSelection().isEmpty();
    }
	public void rootModeChanged(int newMode) {
		fRootMode= newMode;
		if (showWorkingSets() && fWorkingSetModel == null) {
			createWorkingSetModel();
			if (fActionSet != null) {
				fActionSet.getWorkingSetActionGroup().setWorkingSetModel(fWorkingSetModel);
			}
		}
		ISelection selection= fViewer.getSelection();
		Object input= fViewer.getInput();
		boolean isRootInputChange= JavaCore.create(ResourcesPlugin.getWorkspace().getRoot()).equals(input) 
			|| (fWorkingSetModel != null && fWorkingSetModel.equals(input))
			|| input instanceof IWorkingSet;
		try {
			fViewer.getControl().setRedraw(false);
			if (isRootInputChange) {
				fViewer.setInput(null);
			}
			setProviders();
			setSorter();
			fActionSet.getWorkingSetActionGroup().fillFilters(fViewer);
			if (isRootInputChange) {