Bug 241209 [Markers] [Problems View] Changing columns in the preferences makes errors disappear from the view
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/views/markers/ExtendedMarkersView.java
* 
	 * @param markerItem
	 * @param allMarkers
	 */
	private void addAllConcreteItems(MarkerSupportItem markerItem,
			Collection allMarkers) {
		if (markerItem.isConcrete()) {
			allMarkers.add(markerItem);
			return;
		}
		MarkerSupportItem[] children = markerItem.getChildren();
		for (int i = 0; i < children.length; i++) {
			addAllConcreteItems(children[i], allMarkers);
		}
	}
	/**
	 * Add the category to the list of expanded categories.
	 * 
	 * @param category
	 */
	void addExpandedCategory(MarkerCategory category) {
		getCategoriesToExpand().add(category.getName());
	}
	/**
	 * Add all of the markers in markerItem recursively.
	 * 
	 * @param markerItem
	 * @param allMarkers
	 *            {@link Collection} of {@link IMarker}
	 */