Bug 205049 Other plug-ins should be able to define default content generator
Currently only the content generator can define which plug-ins it can be the default for - we need a way for plug-ins to refer back to the marker support for thier own generator.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/provisional/views/markers/MarkerComparator.java
private MarkerField category;
	
	
	private MarkerField[] fields;
	/**
	 * Constant to indicate an ascending sort direction.
	 */
	public static final int ASCENDING = 1;
	/**
	 * Constant to indicate an descending sort direction.
	 */
	public static final int DESCENDING = -1;
	private static final String PRIMARY_SORT_FIELD_TAG = "PRIMARY_SORT_FIELD"; 
	private static final String DESCENDING_FIELDS = "DESCENDING_FIELDS"; 
	
	HashSet descendingFields = new HashSet();
	/**
	 * Create a new instance of the receiver categorised by categoryField
	 * 
	 * @param categoryField
	 *            May be <code>null/<code>
	 * @param mainFields in order of compare significance
	 */