Html父元素高度固定overflow-x为scrol，子元素为左浮动，如何让父元素包容子元素

Html父元素高度固定overflow-x为scrol，子元素为左浮动，如何让父元素包容子元素

这样？？

<style>
    #dv div{float:left;width:300px;height:50px;background:#eee;margin-left:10px}
</style>
<div style="height:200px;overflow-x:auto" id="dv">
    <div style="float:none;width:99999px;background:#fff">
        <div></div><div></div><div></div><div></div><div></div><div></div><div></div><div></div><div></div>
    </div>
</div>

            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content">222</div>
        </div>
    </div>

<div class="container">
        <div class="box">
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content"></div>
            <div class="content">222</div>
        </div>
    </div>