<!DOCTYPE html>
<html>
  <head>
    <title>Basic context-stroke in background-image test</title>
    <style>

div {
  width: 100px;
  height: 100px;
  background-image: url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg'><rect x='5' y='5' width='90' height='90' fill='none' stroke='context-stroke red' stroke-width='10'/></svg>");
  -moz-context-properties: stroke;
  stroke: blue;
}

    </style>
  </head>
  <body>
    <div></div>
  </body>
</html>