Bug 27491 Cannot add classpath variable to project
build id : 200212020010 The buttons OK and extend... are always disabled in the add variable dialog
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/dialogfields/ListDialogField.java
if (fElements.remove(element)) {
			if (fTable != null) {
				fTable.remove(element);
			}
			dialogFieldChanged();
		} else {
			throw new IllegalArgumentException();
		}
	}
	/**
	 * Removes elements from the list.
	 */		
	public void removeElements(List elements) {
		if (elements.size() > 0) {
			fElements.removeAll(elements);
			if (fTable != null) {
				fTable.remove(elements.toArray());
			}
			dialogFieldChanged();
		}
	}
	/**
	 * Gets the number of elements
	 */		
	public int getSize() {
		return fElements.size();
	}
	
	public void selectElements(ISelection selection) {
		fSelectionWhenEnabled= selection;