Bug 219635 [CellEditors] CheckboxEditor flips state when tabbed into
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/CheckboxCellEditor.java
}
    /**
     * Creates a new checkbox cell editor parented under the given control.
     * The cell editor value is a boolean value, which is initially <code>false</code>. 
     * Initially, the cell editor has no cell validator.
     *
     * @param parent the parent control
     * @param style the style bits
     * @since 2.1
     */
    public CheckboxCellEditor(Composite parent, int style) {
        super(parent, style);
    }
    /**
     * The <code>CheckboxCellEditor</code> implementation of
     * this <code>CellEditor</code> framework method simulates
     * the toggling of the checkbox control and notifies
     * listeners with <code>ICellEditorListener.applyEditorValue</code>.
     */
    public void activate() {
        value = !value;
        fireApplyEditorValue();
    }
    /**
     * The <code>CheckboxCellEditor</code> implementation of
     * this <code>CellEditor</code> framework method does
     * nothing and returns <code>null</code>.
     */
    protected Control createControl(Composite parent) {
        return null;