Closes the editor's popup window, discarding all the changes made.
The CancelPopup method is only useful for editors whose popup windows (dropdowns) are not immediately closed after changing their values (e.g. native combo box). Otherwise, the CancelPopup method hides the popup window and discards all the changes made (e.g. checked combo box).
To programmatically hide the editor's popup window and save the changes, use the PopupBaseEdit.ClosePopup method.