Bug 214649 [Markers] Allow markerAttributeGroupings and markerGroups to be specified within contentGenerators
With everything at the top level it is hard to see the relation to a contentGenerator and the groups and attribute groupings. These should be sub elements a la menus.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/internal/MarkerGroup.java
if (typesToMappings.containsKey(type)) {
			EntryMapping defaultMapping = null;
			Iterator mappings = ((Collection) typesToMappings.get(type))
					.iterator();
			while (mappings.hasNext()) {
				EntryMapping mapping = (EntryMapping) mappings.next();
				if (mapping.hasAttributes()) {
					MarkerGroupingEntry entry = mapping.testAttribute(marker);
					if (entry != null) {
						return entry;
					}
				} else {
					
					defaultMapping = mapping;
				}
			}
			if (defaultMapping != null) {
				return defaultMapping.groupingEntry;
			}
		}
		return undefinedEntry;
	}
	/**
	 * Return the field for the receiver.
	 * 
	 * @return {@link IField}
	 */
	public IField getField() {
		return field;
	}