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:           sheet.cssRules.length);
      }
  
      if (browserEngine == BrowserEngine.firefox) {
        sheet.insertRule(
            'input::-moz-selection {'
            '  background-color: transparent;'
  
negative.code: 
      // By default on iOS, Safari would highlight the element that's being tapped
      // on using gray background. This CSS rule disables that.
      if (isWebKit) {
        sheet.insertRule('''
  flt-glass-pane * {
    -webkit-tap-highlight-color: transparent;
  