action_bar.go
func (bar *ActionBar) EditMode(w http.ResponseWriter, r *http.Request) bool {
	return isEditMode(bar.Admin.NewContext(w, r))
}
func (bar *ActionBar) EditMode(w http.ResponseWriter, r *http.Request) bool {
	return isEditMode(bar.Admin.NewContext(w, r))
}
// EditMode return whether current mode is `Preview` or `Edit`