static warnOnce(id, ...args) {
    if (shaka.log.oneTimeWarningIssued_.has(id)) {
      return;
    }

    shaka.log.oneTimeWarningIssued_.add(id);
    shaka.log.alwaysWarn(...args);
  }
This always logs to the console, even in Release mode.  This should only be
used for deprecation messages and things the app should never ignore.

@param {string} id
@param {...*} args