code: void copyTransients(JsMessageImpl copy) {
      super.copyTransients(copy);
      copy.setApproximateLength(approxLength);
      copy.setFluffedSize(fluffedSize);
      return;
    }
docs: /*
  Copies any transient data into the copy of the message passed.
  
  Sub-classes should override this (calling super.copyTransients()) to copy
  any transient cached data into new copies of messages.