overflow：scroll不会向元素添加滚动

Question

我有以下菜单，如果我添加到父div溢出滚动它不帮助我，没有添加滚动。

css结构如下：

<div class="container">

    <div class="navbar-header">
              <a class="logo navbar-btn pull-left" href="/" title="Главная">
          <img src="http://kavaoptom.com.ua/sites/all/themes/mytheme/logo.png" alt="Главная">
        </a>

              <a class="name navbar-brand" href="/" title="Главная">Kava Optom</a>

              <button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
          <span class="sr-only">Toggle navigation</span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span>
        </button>
          </div>

          <div class="navbar-collapse collapse in" aria-expanded="true">
        <nav role="navigation">
                      <ul class="menu nav navbar-nav"><li class="first leaf active-trail active"><a href="/catalog" title="" class="active-trail active">Наши товары</a></li>
<li class="leaf"><a href="/content/%D0%B4%D0%BE%D1%81%D1%82%D0%B0%D0%B2%D0%BA%D0%B0-%D0%B8-%D0%BE%D0%BF%D0%BB%D0%B0%D1%82%D0%B0">Оплата и доставка</a></li>
<li class="leaf"><a href="/content/%D0%BE-%D0%BD%D0%B0%D1%81">О нас</a></li>
<li class="last leaf"><a href="/contact" title="">Контакты</a></li>
<div class="mobile-login"><div></div></div></ul>                    
                      <ul class="menu nav navbar-nav secondary"><li class="first leaf"><a href="/user">Моя учётная запись</a></li>
<li class="last leaf"><a href="/user/logout">Выход</a></li>
</ul>                            </nav>
      </div>
        </div>