bootstrap搜索框自动适应缩放比例

Question

<nav class="navbar navbar-default" role="navigation">    <div class="navbar-header">        <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1">            <span class="sr-only"></span>            <span class="icon-bar"></span>            <span class="icon-bar"></span>            <span class="icon-bar"></span>        </button>    </div>    <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">        <ul class="nav navbar-nav">            <li class="dropdown">                <a href="Area.html">成都市 <b class="glyphicon glyphicon-menu-down"></b></a>            </li>        </ul>        <form class="navbar-form navbar-left" role="search-box">            <input type="text" class="form-control"  onclick="javascript:window.location.href='Search.html';"  placeholder="职位搜索">        </form>        <ul class="nav navbar-nav navbar-right">            <li class="dropdown">                <a href="#" class="dropdown-toggle" data-toggle="dropdown">筛选<b class="glyphicon glyphicon-list"></b></a>            </li>        </ul>        <div class="clearfix"></div>    </div></nav>