The Tor Browser / file revision

 <?xml version="1.0"?>

 <?xml-stylesheet href="chrome://global/skin/" type="text/css"?>

 <window id="test-canvas" title="Canvas in XUL test"

         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"

         xmlns:html="http://www.w3.org/1999/xhtml" onload="workWithCanvas();">

   <script type="text/javascript">

     function workWithCanvas()

     {

       var c = document.getElementById("canvas");

       var ctx = c.getContext("2d");

       ctx.fillStyle = "#ff0000";

       ctx.fillRect(0, 0, 100, 100);

     }

   </script>

   <html:canvas id="canvas" width="100" height="100"

                style="width: 100px; height: 100px; max-height: 100px; max-width: 100px;"/>

 </window>