UIVideoEditorControllerの「保存」のテキスト変更 ref: http://qiita.com/MTattin/items/a4563ce8e55dc0919c54

file0.swift

///
/// CstmVideoEditorController
///
class CstmVideoEditorController: UIVideoEditorController {
    ///
    /// will appear
    ///
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        for v in self.navigationBar.subviews {
            if v is UIButton {
                ///
                /// 右側のボタンか判定
                ///
                if v.frame.origin.x > self.view.w * 0.5 {
                    (v as! UIButton).setTitle("Done", for: UIControlState.normal)
                    (v as! UIButton).setTitle("Done", for: UIControlState.disabled)
                    (v as! UIButton).setTitle("Done", for: UIControlState.selected)
                    (v as! UIButton).setTitle("Done", for: UIControlState.highlighted)
                }
            }
        }
    }
}