Bug 32664 Package Explorer: hierarchical layout and back-linking don't work allways together.
The following triggers it: - initially 'flat layout' is used, 'link with editor' is on or off - open a java file - use 'collapse all' in the package explorer - select 'hierarchical layout' - switch 'link with editor' on or off&on -> no back-linking
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerContentProvider.java
for (int i= 0; i < deltas.length; i++) {
			if (processResourceDelta(deltas[i], parent))
				return true;
		}
		return false;
	}
	
	private void postRefresh(final Object root) {
		postRefresh(root, true);
	}
	
	private void postRefresh(final Object root, final boolean updateLabels) {
		postRunnable(new Runnable() {
			public void run() {
				Control ctrl= fViewer.getControl();
				if (ctrl != null && !ctrl.isDisposed()){
					fViewer.refresh(root, updateLabels);
				}
			}
		});
	}
	private void postAdd(final Object parent, final Object element) {
		postRunnable(new Runnable() {
			public void run() {
				Control ctrl= fViewer.getControl();
				if (ctrl != null && !ctrl.isDisposed()){
					fViewer.add(parent, element);
				}
			}
		});