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
private int getLayoutAsInt() {
		if (fIsCurrentLayoutFlat)
			return FLAT_LAYOUT;
		else
			return HIERARCHICAL_LAYOUT;
	}
	protected void saveScrollState(IMemento memento, Tree tree) {
		ScrollBar bar= tree.getVerticalBar();
		int position= bar != null ? bar.getSelection() : 0;
		memento.putString(TAG_VERTICAL_POSITION, String.valueOf(position));
		
		bar= tree.getHorizontalBar();
		position= bar != null ? bar.getSelection() : 0;
		memento.putString(TAG_HORIZONTAL_POSITION, String.valueOf(position));
	}
	protected void saveSelectionState(IMemento memento) {
		Object elements[]= ((IStructuredSelection) fViewer.getSelection()).toArray();
		if (elements.length > 0) {
			IMemento selectionMem= memento.createChild(TAG_SELECTION);
			for (int i= 0; i < elements.length; i++) {
				IMemento elementMem= selectionMem.createChild(TAG_ELEMENT);
				
				Object o= elements[i];
				if (o instanceof IJavaElement)
					elementMem.putString(TAG_PATH, ((IJavaElement) elements[i]).getHandleIdentifier());
			}
		}
	}
	protected void saveExpansionState(IMemento memento) {
		Object expandedElements[]= fViewer.getVisibleExpandedElements();