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/MarkerPriorityField.java
static final String HIGH_PRIORITY_IMAGE_PATH = "$nl$/icons/full/obj16/hprio_tsk.gif"; 
	static final String LOW_PRIORITY_IMAGE_PATH = "$nl$/icons/full/obj16/lprio_tsk.gif"; 
	/**
	 * Return a new priority field.
	 */
	public MarkerPriorityField() {
		super();
	}
	/*
	 * (non-Javadoc)