Bug 305703 [Viewers][CommonNavigator] remembered contributions can leak when using filters
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
CustomHashtable expanded = newHashtable(CustomHashtable.DEFAULT_CAPACITY); 
																					
																					
																					
																					
		for (int i = 0; i < items.length; ++i) {
			if (getExpanded(items[i])) {
				Object element = items[i].getData();
				if (element != null) {
					expanded.put(element, element);
				}
			}
		}
		int min = Math.min(elementChildren.length, items.length);
		
		
		int numItemsToDispose = items.length - min;
		if (numItemsToDispose > 0) {
			CustomHashtable children = newHashtable(elementChildren.length * 2);
			for (int i = 0; i < elementChildren.length; i++) {
				Object elementChild = elementChildren[i];
				children.put(elementChild, elementChild);
			}
			int i = 0;
			while (numItemsToDispose > 0 && i < items.length) {
				Object data = items[i].getData();
				if (data == null || items.length - i <= numItemsToDispose || !children.containsKey(data)) {
					if (data != null) {
						disassociate(items[i]);
					}