It is also possible to use some external js bookmarklet in any file to show some minimal information.
javascript:(function(){var script=document.createElement('script');script.onload=function(){var stats=new Stats();document.body.appendChild(stats.dom);requestAnimationFrame(function loop(){stats.update();requestAnimationFrame(loop)});};script.src='//mrdoob.github.io/stats.js/build/stats.min.js';document.head.appendChild(script);})()