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
Item[] items = getChildren(parent);
	        for (int i = 0; i < items.length; i++) {
	            Item item = items[i];
	            Object data = item.getData();
	            if (data != null && equals(data, element))
	                return item;
	        }
	        return null;
	    }
		private CustomHashtable createRootAccessedMap(TreePath[] paths) {
			CustomHashtable result= new CustomHashtable(getComparer());
			for (int i= 0; i < paths.length; i++) {
				TreePath path= paths[i];
				Object root= path.getFirstSegment();
				if (root != null) {
					result.put(root, path);
				}
			}
			return result;
		}
	}
 
	/* (non-Javadoc)
	 * Method declared on IViewPart.
	 */
	private boolean fLinkingEnabled;
    public void init(IViewSite site, IMemento memento) throws PartInitException {
		super.init(site, memento);
		fMemento= memento;
		restoreRootMode(fMemento);