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
saveLinkingEnabled(memento);
		
		
		fActionSet.saveFilterAndSorterState(memento);
	}
	
	private void saveCurrentFrame(IMemento memento) {
        FrameAction action = fActionSet.getUpAction();
        FrameList frameList= action.getFrameList();
		if (frameList.getCurrentIndex() > 0) {
			TreeFrame currentFrame = (TreeFrame) frameList.getCurrentFrame();
			
			if (currentFrame.getInput() instanceof WorkingSetModel)
				return;
			IMemento frameMemento = memento.createChild(TAG_CURRENT_FRAME);
			currentFrame.saveState(frameMemento);
		}
	}
	private void saveLinkingEnabled(IMemento memento) {
		memento.putInteger(PreferenceConstants.LINK_PACKAGES_TO_EDITOR, fLinkingEnabled ? 1 : 0);
	}
	private void saveLayoutState(IMemento memento) {
		if (memento != null) {	
			memento.putInteger(TAG_LAYOUT, getLayoutAsInt());
		} else {
		
			IPreferenceStore store= JavaPlugin.getDefault().getPreferenceStore();
			store.setValue(TAG_LAYOUT, getLayoutAsInt());
		}
	}