Bug 273489 [Mac] We should not nest sheets
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/PathVariableDialog.java
/**
     * The value of the variable being edited.
     */
    private String variableValue;
    /**
     * The original name of the variable being edited. It is used when testing
     * if the current variable's name is already in use.
     */
    private String originalName;
    /**
     * Used to select the proper message depending on the current mode
     * (new/existing variable).
     */
    private boolean newVariable;
    /**
     * Reference to the path variable manager. It is used for validating
     * variable names.
     */
    private IPathVariableManager pathVariableManager;
    /**
     * Set of variable names currently in use. Used when warning the user that
     * the currently selected name is already in use by another variable.
     */
    private Set namesInUse;
    /**
     * The current validation status. Its value can be one of the following:<ul>
     * <li><code>IMessageProvider.NONE</code> (default);</li>
     * <li><code>IMessageProvider.WARNING</code>;</li>
     * <li><code>IMessageProvider.ERROR</code>;</li>
     * </ul>