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
fActionSet.getForwardAction().update();
	}
	/**
	 * This viewer ensures that non-leaves in the hierarchical
	 * layout are not removed by any filters.
	 * 
	 * @since 2.1
	 */
	private ProblemTreeViewer createViewer(Composite composite) {
		return  new PackageExplorerProblemTreeViewer(composite, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL);
	}
	/**
	 * Answers whether this part shows the packages flat or hierarchical.
	 * 
	 * @since 2.1
	 */
	public boolean isFlatLayout() {
		return fIsCurrentLayoutFlat;
	}
	
	private void setProviders() {
		
		fContentProvider= createContentProvider();
		fContentProvider.setIsFlatLayout(fIsCurrentLayoutFlat);
		fViewer.setComparer(createElementComparer());
		fViewer.setContentProvider(fContentProvider);
	
		fLabelProvider= createLabelProvider();
		fLabelProvider.setIsFlatLayout(fIsCurrentLayoutFlat);
		fViewer.setLabelProvider(new DecoratingJavaLabelProvider(fLabelProvider, false));