>>556
.tabbrowser-tab[bursting] .tab-icon-image {
animation: hoge .4s ease-in-out !important;
}
@keyframes hoge {
0% {
transform: rotate(0deg);
}
50% {
transform: rotate(90deg);
}
100% {
transform: rotate(-90deg);
}
}

参考にしたページ
https://mamewaza.com/support/blog/20150424.html
https://qiita.com/7968/items/1d999354e00db53bcbd8