static simplyCached NavigableMap<S> emojiShortNameMap() {
  NavigableMap<S> map = ciMap();
  for (Map m : rawEmojisList()) {
    S shortName = cast m.get("shortname");
    S emoji = cast m.get("emoji");
    if (startsWith(shortName, ":"))
      map.put(shortName, emoji);
  }
  ret map;
}

Began life as a copy of #1029673