Bug 214137 [Markers] Unbound system filters should be bound to problems view.
In 3.3 we supported systemFilters which are not currently picked up by the problems view. We should pick these up for compatiblity.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/views/markers/CachedMarkerBuilder.java
if (getCategoryGroup() != null)
				field = getCategoryGroup().getMarkerField();
			comparator = new MarkerComparator(field, generator.getAllFields());
			comparator.restore(this.memento);
		}
		return comparator;
	}
	/**
	 * Return the elements in the adapter.
	 * 
	 * @return Object[]
	 */
	MarkerItem[] getElements() {
		if (refreshingMarkers()) {
			return MarkerSupportInternalUtilities.EMPTY_MARKER_ITEM_ARRAY;
		}
		if (isShowingHierarchy() && categories != null) {
			return categories;
		}
		return currentMap.toArray();
	}
	/**
	 * Return the currently enabled filters.
	 * 
	 * @return Collection of MarkerFieldFilterGroup
	 */
	Collection getEnabledFilters() {
		if (enabledFilters == null) {
			enabledFilters = new HashSet();
			Iterator filtersIterator = getAllFilters().iterator();