anchor.diff:    left: 0;
   }''', sheet.cssRules.length);
   
  -    if (browserEngine == BrowserEngine.webkit) {
  +    if (isWebKit) {
         sheet.insertRule(
             'flt-semantics input[type=range]::-webkit-slider-thumb {'
             '  -webkit-appearance: none;'
  
positive.code:     // is 1.0.
      window.debugOverrideDevicePixelRatio(1.0);
  
      if (html.window.visualViewport == null &&
          browserEngine == BrowserEngine.webkit) {
        // Safari sometimes gives us bogus innerWidth/innerHeight values when the
        // page loads. When it changes the values to correct ones it does not
        // notify of the change via `onResize`. As a workaround, we setup a
  
negative.code: 
      // This undoes browser's default layout attributes for paragraphs. We
      // compute paragraph layout ourselves.
      if (isFirefox) {
        // For firefox set line-height, otherwise textx at same font-size will
        // measure differently in ruler.
        sheet.insertRule(
            'flt-ruler-host p, flt-scene p '
            '{ margin: 0; line-height: 100%;}',
            sheet.cssRules.length);
      } else {
        sheet.insertRule(
            'flt-ruler-host p, flt-scene p '
            '{ margin: 0; }',
            sheet.cssRules.length);
      }
  
      // This undoes browser's default painting and layout attributes of range
      // input, which is used in semantics.
  