How to make Chrome redraw SVG dynamically added content?

I've dynamacally added the circle elements to the svg displayed in a iFrame. Chrome isnt showing the new elements, not tried FF yet. Is there somekind of redraw/refresh I need to call? The first circle is actually in the svg document, the rest come from script.

<iframe id="svgFrame" src="xmlfile1.svg" width="300" height="300">
<svg xmlns="http://www.w3.org/2000/svg" id="SVG1" width="200" height="200">
   <circle cx="20" cy="20" r="5"/>
   <circle cx="165" cy="80" r="32"/>
   <circle cx="15" cy="38" r="32"/>
   <circle cx="140" cy="39" r="30"/>
   <circle cx="178" cy="32" r="22"/>
   ...etc
   <circle cx="166" cy="130" r="16"/>
</svg>
</iframe>

The javascript which creates the elements:

function RandomNumber(min, max) {
    var r;
    r = Math.floor(Math.random() * (max - min + 1)) + min;
    return r;
}

var svg = document.getElementById("svgFrame").contentDocument;

for (var i = 0; i < 99; i++) {

    var n = svg.createElement("circle");
    n.setAttribute("cx" , RandomNumber( 0 , 200) );
    n.setAttribute("cy" , RandomNumber(0, 200) );
    n.setAttribute("r"  , RandomNumber(5, 35) );

    svg.documentElement.appendChild(n);
}