Bug 221337 [Markers] MarkerItem has too much API
We are exposing too much as API in MarkerItem. We should only provide getAtttributeValue and the methods that support PATH_ATTRIBUTE and NAME_ATTRIBUTE as they are tricky. Everything else needs to be pushed down to an internal class. We should mention the relevant IMarker constants for those removed.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/views/markers/MarkerDescriptionField.java
* Return the collation key for the description.
	 * 
	 * @param element
	 * @return CollationKey
	 */
	private CollationKey getDescriptionKey(Object element) {
		if (element instanceof MarkerEntry)
			return ((MarkerItem) element).getCollationKey(IMarker.MESSAGE,
					MarkerSupportConstants.EMPTY_STRING);
		return MarkerSupportInternalUtilities.EMPTY_COLLATION_KEY;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.internal.provisional.views.markers.MarkerField#getValue(org.eclipse.ui.internal.provisional.views.markers.MarkerItem)
	 */
	public String getValue(MarkerItem item) {
		return item.getAttributeValue(IMarker.MESSAGE,
				MarkerSupportConstants.EMPTY_STRING);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.internal.provisional.views.markers.api.MarkerField#getEditingSupport()
	 */
	public EditingSupport getEditingSupport(ColumnViewer viewer) {
		return new DescriptionEditingSupport(viewer);
	}
}