function render_callback() {
                layer.drawImage(0, 0, video);
                if (!video.ended)
                    window.setTimeout(render_callback, 20);
            }
Plays the video at the specified URL within this layer. The video
will be loaded automatically, and this and any future operations will
wait for the video to finish loading. Future operations will not be
executed until the video finishes playing.

@param {Guacamole.Layer} layer The layer to draw upon.
@param {String} mimetype The mimetype of the video to play.
@param {Number} duration The duration of the video in milliseconds.
@param {String} url The URL of the video to play.