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
newMarkers.getSize() - 1, 0);
			if (monitor.isCanceled())
				return;
			categories = newCategories;
		}
		monitor.worked(50);
		currentMap = newMarkers;
	}
	/**
	 * Add group to the enabled filters.
	 * 
	 * @param group
	 */
	void toggleFilter(MarkerFieldFilterGroup group) {
		Collection enabled = getEnabledFilters();
		if (enabled.remove(group)) 
			group.setEnabled(false);
		else {
			group.setEnabled(true);
			enabled.add(group);
		}
		writeFiltersPreference();
		scheduleMarkerUpdate();
	}
	/**
	 * Update the focus resources from list. If there is an update required
	 * return <code>true</code>. This method assumes that there are filters
	 * on resources enabled.
	 * 
	 * @param elements