docs: private WsByteBuffer[] marshallAddedHeaders(WsByteBuffer[] inBuffers, int index) {
          WsByteBuffer[] buffers = inBuffers;
          buffers[index] = allocateBuffer(this.outgoingHdrBufferSize);
          for (HeaderElement elem = this.hdrSequence; null != elem; elem = elem.nextSequence) {
              if (elem.wasAdded()) {
                  buffers = marshallHeader(buffers, elem);
              }
          }
          // add second EOL
          buffers = putBytes(BNFHeaders.EOL, buffers);
          buffers = flushCache(buffers);
          // flip the last buffer now that we're done
          buffers[buffers.length - 1].flip();
          return buffers;
      }