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/MarkerContentGenerator.java
Collection allFieldList = new ArrayList();
		Collection visibleFieldList = new ArrayList();
		for (int i = 0; i < elements.length; i++) {
			MarkerField field = registry.getField(elements[i]
					.getAttribute(MarkerSupportConstants.ATTRIBUTE_ID));
			if (field == null)
				continue;
			allFieldList.add(field);
			if (!VALUE_FALSE
					.equals(elements[i].getAttribute(ATTRIBUTE_VISIBLE)))
				visibleFieldList.add(field);
		}
		allFields = new MarkerField[allFieldList.size()];
		allFieldList.toArray(allFields);
		visibleFields = new MarkerField[visibleFieldList.size()];
		visibleFieldList.toArray(visibleFields);
	}
	/**
	 * Return whether or not we are showing a hierarchy,.
	 * 
	 * @return <code>true</code> if a hierarchy is being shown.
	 */
	public boolean isShowingHierarchy() {
		return categoryGroup != null;
	}
	/**
	 * Load the filters preference.
	 */
	private void loadFiltersPreference() {
		String mementoString = IDEWorkbenchPlugin.getDefault()