Bug 208052 [Markers] Tasks does not sort by completion
Sorting by the completion currently does nothing.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/provisional/views/markers/MarkerCompletionField.java
static final String COMPLETE_IMAGE_PATH = "$nl$/icons/full/obj16/complete_tsk.gif"; 
	static final String INCOMPLETE_IMAGE_PATH = "$nl$/icons/full/obj16/incomplete_tsk.gif"; 
	/**
	 * Create a new instance of the receiver.
	 */
	public MarkerCompletionField() {
		super();