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
if (showWorkingSets()) {
			createWorkingSetModel();
		}
		restoreLayoutState(memento);
	}
	private void restoreRootMode(IMemento memento) {
		if (memento != null) {
			Integer value= fMemento.getInteger(TAG_ROOT_MODE);
			fRootMode= value == null ? ViewActionGroup.SHOW_PROJECTS : value.intValue();
			if (fRootMode != ViewActionGroup.SHOW_PROJECTS && fRootMode != ViewActionGroup.SHOW_WORKING_SETS)
				fRootMode= ViewActionGroup.SHOW_PROJECTS;
		} else {
			fRootMode= ViewActionGroup.SHOW_PROJECTS;
		}
	}
	private void restoreLayoutState(IMemento memento) {
		Integer state= null;
		if (memento != null)
			state= memento.getInteger(TAG_LAYOUT);
		
		if(state == null) {
			IPreferenceStore store= JavaPlugin.getDefault().getPreferenceStore();
			state= new Integer(store.getInt(TAG_LAYOUT));
		}
		if (state.intValue() == FLAT_LAYOUT)
			fIsCurrentLayoutFlat= true;
		else if (state.intValue() == HIERARCHICAL_LAYOUT)
			fIsCurrentLayoutFlat= false;
		else
			fIsCurrentLayoutFlat= true;