private String formatTimestamp(String s) {
    String str = s;
    if (str.contains("E")) {
      str = "1" + str.substring(str.indexOf(".") + 1, str.indexOf("E"));
    }
    if (str.length() > 13) {
      str = str.substring(0, 13);
    }
    return str;
  }
format 1.536834943435905E12 (nano seconds) to 1536834943435 (ms)
and convert timestamp to milliseconds

@param s raw String obtained from getStats.

@return the formatted timestamp
KITE-Framework/src/main/java/org/webrtc/kite/stats/rtc/RTCSingleStatObject.java