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
boolean enabled= isEnabled();
		if (isOkToUse(fTableControl)) {
			if (!enabled) {
				fSelectionWhenEnabled= fTable.getSelection();
				selectElements(null);
			} else {
				selectElements(fSelectionWhenEnabled);
				fSelectionWhenEnabled= null;
			}
			fTableControl.setEnabled(enabled);
		}
		updateButtonState();
	}
	/**
	 * Sets a button enabled or disabled.
	 */	
	public void enableButton(int index, boolean enable) {
		if (fButtonsEnabled != null && index < fButtonsEnabled.length) {
			fButtonsEnabled[index]= enable;
			updateButtonState();
		}
	}
	
	private boolean isButtonEnabled(ISelection sel, int index) {
		boolean extraState= getManagedButtonState(sel, index);
		return isEnabled() && extraState && fButtonsEnabled[index];
	}