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/TypeMarkerGroup.java
/**
	 * TypeMarkerField is the MarkerField used for MarkerGroupungs
	 * 
	 * @since 3.4
	 * 
	 */
	class TypeMarkerField extends GroupMarkerField {
		/**
		 * Create a new instance of the receiver.
		 * @param group
		 */
		TypeMarkerField(MarkerGroup group) {
			super(group);
		}
		/*
		 * (non-Javadoc)
		 * 
		 * @see org.eclipse.ui.internal.provisional.views.markers.api.MarkerField#getValue(org.eclipse.ui.internal.provisional.views.markers.api.MarkerItem)
		 */
		public String getValue(MarkerItem item) {
			if (item.isConcrete()) {
				IMarker marker = item.getMarker();
				if (marker == null || !marker.exists())
					return MarkerMessages.FieldCategory_Uncategorized;
				String groupName = MarkerSupportRegistry.getInstance()
						.getCategory(marker);
				if (groupName == null) {