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/internal/views/markers/MarkerContentGenerator.java
static final Object CACHE_UPDATE_FAMILY = new Object();
	private static final String ELEMENT_MARKER_FIELD_FILTER_GROUP = "markerFieldFilterGrouping"; 
	private static final IResource[] EMPTY_RESOURCE_ARRAY = new IResource[0];
	private static final String MARKER_FIELD_REFERENCE = "markerFieldReference"; 
	private MarkerField[] allFields;
	private IConfigurationElement configurationElement;
	private Collection markerTypes;
	private MarkerField[] initialVisible;
	private Collection groups;
	/**
	 * Create a new MarkerContentGenerator
	 * 
	 * @param element
	 */
	public MarkerContentGenerator(IConfigurationElement element) {
		configurationElement = element;
	}
	/**
	 * Add the groups defined in the receiver to the collection of groups.
	 * 
	 * @param groups
	 */
	private void addDefinedGroups(Collection groups) {
		IConfigurationElement[] groupings = configurationElement
				.getChildren(MarkerSupportRegistry.MARKER_GROUPING);
		for (int i = 0; i < groupings.length; i++) {
			groups.add(new MarkerGroup(groupings[i]));
		}
	}
	/**