function focusEditor() {
        DeprecationWarning.deprecationWarning("Use MainViewManager.focusActivePane() instead of EditorManager.focusEditor().", true);
        MainViewManager.focusActivePane();
    }
Returns focus to the last visible editor that had focus. If no editor visible, does nothing.
This function should be called to restore editor focus after it has been temporarily
removed. For example, after a dialog with editable text is closed.