<!DOCTYPE html>
<embed type="application/x-test" width="200" height="200"></embed>
<script>
var plugin = document.querySelector("embed");
onload = function() {
  plugin.startAudioPlayback();
};
function stopAudio() {
  plugin.stopAudioPlayback();
}
function pluginMuted() {
  return plugin.audioMuted();
}
function toggleMuteState(muted) {
  var Ci = SpecialPowers.Ci;
  var utils = SpecialPowers.wrap(window).top
                           .QueryInterface(Ci.nsIInterfaceRequestor)
                           .getInterface(Ci.nsIDOMWindowUtils);
  utils.audioMuted = muted;
}
</script>