Firefox userChrome.css for showing tab close button on hover, even tho tab is inactive

hover-tab-close.js

/* move favicon, throbber and text to the right so that the close button appears on the left */
.tabbrowser-tab .tab-icon-image {
  -moz-box-ordinal-group: 2 !important;
}
 
.tabbrowser-tab .tab-throbber {
  -moz-box-ordinal-group: 2 !important;
}
 
.tabbrowser-tab .tab-label {
  -moz-box-ordinal-group: 3 !important;
}
 
/* hide close button initially */
.tabbrowser-tab .tab-close-button {
  display: none !important;
}
 
/* show close + hide throbber & favicon on hover */
.tabbrowser-tab:hover .tab-close-button {
  display: block !important;
}
 
.tabbrowser-tab:hover .tab-icon-image {
  display: none !important;
}
 
.tabbrowser-tab:hover .tab-throbber {
  display: none !important;
}
 
/* app tabs should not behave like regular tabs, so let them stay normal (viz. don't show close on hover) */
.tabbrowser-tab[pinned]:hover .tab-close-button {
  display: none !important;
}
 
.tabbrowser-tab[pinned]:hover .tab-icon-image {
  display: block !important;
}