Why the Ext.panel.Panel can't show autoScroll when use to show the SVG str?

If use normal html str,that ok ,it can show the vertical scroll,but when use

the svg str, it can not show the scroll !

The code I test like below, Somebody know whether the panel can show scroll when show svg?

or their some way to config?

Code:

Ext.onReady(function() {
 
 var svg_str = '<svg width="100%" height="100%" version="1.1"' +
  'xmlns="http://ift.tt/nvqhV5">' +

 '<text id="XPos" x="50" y="50">X Position :</text>' +
 '<text id="YPos" x="50" y="70">Y Position :</text>' +
 '<text id="ClickPos" x="50" y="90">Last Click made at : </text>' +
 '<rect x="50" y="100" width="200" height="1200" style="fill:blue" ' + 
 '</svg> ';
 
 
 var normal_str =  '<p>World!</p> <p>World!</p><p>World!</p><p>World!</p>  <p>World!</p> <p>World!</p> <p>World!</p> <p>World!</p><p>World!</p><p>World!</p><p>World!</p> <p>World!</p> <p>World!</p>';
  
 
 var constrainedWin, constrainedWin2,drawComponent;
 var win2 = Ext.create('Ext.panel.Panel', {
     height: 300,
     width: 800,
     //x: 450,
    // y: 450,
     title: 'test111',
     closable: false,
     plain: true,
     layout: 'fit',
     renderTo:Ext.getBody(),
     closable:true,
     html:svg_str,
     resizable:true,
     autoScroll:true,
 
 });
                
});