Bug 214492 [Markers] Need to be able to add filters to existing markers views
Currently you can only add filters to a new markerContentProvider. We need to able to bind them to existing markerContentProviders as well.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/internal/MarkerGroup.java
} else {
					IDEWorkbenchPlugin.log(NLS.bind(
							"Reference to invaild markerGroupingEntry {0}", 
							defaultEntryId));
				}
			}
		}
	}
	/**
	 * Create the fields for the marker views.
	 */
	protected void createFields() {
		field = new FieldGroup(this);
		markerField = new GroupMarkerField(this);
	}
	/**
	 * Add the entry for the markerType.
	 * 
	 * @param markerType
	 * @param entry
	 */
	private void addEntry(String markerType, EntryMapping entry) {
		MarkerType[] allDerived = getMarkerTypes(markerType);
		for (int i = 0; i < allDerived.length; i++) {
			Collection entries = new HashSet();
			MarkerType type = allDerived[i];
			if (typesToMappings.containsKey(type.getId())) {
				entries = (Collection) typesToMappings.get(markerType);
			} else {
				entries = new HashSet();