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
for (int i= 0; i < current.length; i++) {
				if (!newSelection.contains(current[i]))
					return false;
			}
	    	return true;
	    }
	    
	    private boolean fInPreserveSelection;
		protected void preservingSelection(Runnable updateCode) {
			try {
				fInPreserveSelection= true;
				super.preservingSelection(updateCode);
			} finally {
				fInPreserveSelection= false;
			}
		}
		protected void setSelectionToWidget(ISelection selection, boolean reveal) {
			if (!fInPreserveSelection || !(selection instanceof MultiElementSelection)) {
				super.setSelectionToWidget(selection, reveal);
				return;
			}
			IContentProvider cp= getContentProvider();
			if (!(cp instanceof IMultiElementTreeContentProvider)) {
				super.setSelectionToWidget(selection, reveal);
				return;
			}
			IMultiElementTreeContentProvider contentProvider= (IMultiElementTreeContentProvider)cp;
			MultiElementSelection toRestore= (MultiElementSelection)selection;
			List pathsToSelect= new ArrayList();
			for (Iterator iter= toRestore.iterator(); iter.hasNext();) {