Bug 44861 [CellEditors] DialogCellEditor does not handle focusLost()
Make sure you have org.eclipse.ui.examples.propertysheet_2.1.0 and open any *.usr file. Select "Richard" from the outline view and select "eyecolor" from the properties view (notice the ... button). Now open the search dialog and notice the ... button is still there. If you select other text or combo properties, notice the editor has been deactivated.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/DialogCellEditor.java
* @return the selected value, or <code>null</code> if the dialog was 
     *   cancelled or no selection was made in the dialog
     */
    protected abstract Object openDialogBox(Control cellEditorWindow);
    /**
     * Updates the controls showing the value of this cell editor.
     * <p>
     * The default implementation of this framework method just converts
     * the passed object to a string using <code>toString</code> and
     * sets this as the text of the label widget.
     * </p>
     * <p>
     * Subclasses may reimplement.  If you reimplement this method, you
     * should also reimplement <code>createContents</code>.
     * </p>
     *
     * @param value the new value of this cell editor
     */
    protected void updateContents(Object value) {
        if (defaultLabel == null) {
			return;
		}
        String text = "";
        if (value != null) {
			text = value.toString();
		}
        defaultLabel.setText(text);
    }
}