>>>
const _urlAttributes = const [
  'action', '_action',          // in form
  'background', '_background',  // in body
  'cite', '_cite',              // in blockquote, del, ins, q
  'data', '_data',              // in object
  'formaction', '_formaction',  // in button, input
  'href', '_href',              // in a, area, link, base, command
  'icon', '_icon',              // in command
  'manifest', '_manifest',      // in html
  'poster', '_poster',          // in video
  'src', '_src',                // in audio, embed, iframe, img, input, script,
                                //    source, track,video
];
<<<
const _urlAttributes = const [
  'action',
  '_action', // in form
  'background',
  '_background', // in body
  'cite',
  '_cite', // in blockquote, del, ins, q
  'data',
  '_data', // in object
  'formaction',
  '_formaction', // in button, input
  'href',
  '_href', // in a, area, link, base, command
  'icon',
  '_icon', // in command
  'manifest',
  '_manifest', // in html
  'poster',
  '_poster', // in video
  'src',
  '_src', // in audio, embed, iframe, img, input, script,
  //    source, track,video
];