public JBCefClient addKeyboardHandler(@NotNull CefKeyboardHandler handler, @NotNull CefBrowser browser) {
    return myKeyboardHandler.add(handler, browser, () -> {
      myCefClient.addKeyboardHandler(new CefKeyboardHandler() {
        @Override
        public boolean onPreKeyEvent(CefBrowser browser, CefKeyEvent event, BoolRef is_keyboard_shortcut) {
          return myKeyboardHandler.handleBooleanReturnAnyOf(browser, handler -> {
            return handler.onPreKeyEvent(browser, event, is_keyboard_shortcut);
          });
        }

        @Override
        public boolean onKeyEvent(CefBrowser browser, CefKeyEvent event) {
          return myKeyboardHandler.handleBooleanReturnAnyOf(browser, handler -> {
            return handler.onKeyEvent(browser, event);
          });
        }
      });
    });
  }
public JBCefClient addKeyboardHandler(@NotNull CefKeyboardHandler handler, @NotNull CefBrowser browser)