css下拉菜单在dojo dijit.layout.ContentPane中不浮动

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/dojo/1.16.4/dijit/themes/claro/claro.css">
<script src="https://cdn.jsdelivr.net/npm/dojo/1.16.4/dojo/dojo.js"></script>

<div id="myContentPane" data-dojo-type="dijit/layout/ContentPane" style="width: 200px; height: 200px;"></div>

require(["dojo/parser", "dijit/Menu", "dijit/MenuItem", "dijit/form/DropDownButton", "dojo/domReady!"], function(parser){
    parser.parse();
    
    var myMenu = new dijit.Menu({
        style: "display: none;"
    });
    
    myMenu.addChild(new dijit.MenuItem({
        label: "Option 1",
        onClick: function(){
            // 处理选项1的点击事件
        }
    }));
    
    myMenu.addChild(new dijit.MenuItem({
        label: "Option 2",
        onClick: function(){
            // 处理选项2的点击事件
        }
    }));
    
    var dropDownButton = new dijit.form.DropDownButton({
        label: "Menu",
        dropDown: myMenu
    }, "myContentPane");
});