docs: static String cssContent(String token) {
      int n = token.length();
      int pos = 0;
      StringBuilder sb = null;
      if (n >= 2) {
        char ch0 = token.charAt(0);
        if (ch0 == '"' || ch0 == '\'') {
          if (ch0 == token.charAt(n - 1)) {
            pos = 1;
            --n;
            sb = new StringBuilder(n);
          }
        }
      }
      for (int esc; (esc = token.indexOf('\\', pos)) >= 0;) {
        int end = esc + 2;
        if (esc > n) { break; }
        if (sb == null) { sb = new StringBuilder(n); }
        sb.append(token, pos, esc);
        int codepoint = token.charAt(end - 1);
        if (isHex(codepoint)) {
          // Parse \hhhhh<opt-break> where hhhhh is one or more hex digits
          // and <opt-break> is an optional space or tab character that can be
          // used to separate an escape sequence from a following literal hex
          // digit.
          while (end < n && isHex(token.charAt(end))) { ++end; }
          try {
            codepoint = Integer.parseInt(token.substring(esc + 1, end), 16);
          } catch (RuntimeException ex) {
            ignore(ex);
            codepoint = 0xfffd;  // Unknown codepoint.
          }
          if (end < n) {
            char ch = token.charAt(end);
            if (ch == ' ' || ch == '\t') {  // Ignorable hex follower.
              ++end;
            }
          }
        }
        sb.appendCodePoint(codepoint);
        pos = end;
      }
      if (sb == null) { return token; }
      return sb.append(token, pos, n).toString();
    }