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
FrameList frameList= action.getFrameList();
			TreeFrame frame = new TreeFrame(fViewer);
			frame.restoreState(frameMemento);
			frame.setName(getFrameName(frame.getInput()));
			frame.setToolTipText(getToolTipText(frame.getInput()));
			frameList.gotoFrame(frame);
		}
	}
	private void restoreLinkingEnabled(IMemento memento) {
		Integer val= memento.getInteger(PreferenceConstants.LINK_PACKAGES_TO_EDITOR);
		if (val != null) {
			fLinkingEnabled= val.intValue() != 0;
		}
	}
	protected void restoreScrollState(IMemento memento, Tree tree) {
		ScrollBar bar= tree.getVerticalBar();
		if (bar != null) {
			try {
				String posStr= memento.getString(TAG_VERTICAL_POSITION);
				int position;
				position= new Integer(posStr).intValue();
				bar.setSelection(position);
			} catch (NumberFormatException e) {
				
			}
		}
		bar= tree.getHorizontalBar();
		if (bar != null) {
			try {
				String posStr= memento.getString(TAG_HORIZONTAL_POSITION);