Counter = 0;
const stylesheetText = makeStyle();
let stylesheet = new CSSStyleSheet();

PerfTestRunner.measureTime({
    description: 'Performance of parsing many invalid declarations',
    run: () => {
      // This is a parsing test: we don't care about style recalc.
      // We append a rule based on globalCounter to prevent caching
      // on the stylesheet string.
      stylesheet.replaceSync(stylesheetText + `\n .b${globalCounter++} {}`);
      style.textContent = stylesheetText;
    }
});

</script>