void addSize(RpcCallContext context, Result r) {
    if (context != null && r != null && !r.isEmpty()) {
      for (Cell c : r.rawCells()) {
        context.incrementResponseCellSize(PrivateCellUtil.estimatedSerializedSizeOf(c));
      }
    }
  }
Method to account for the size of retained cells.
@param context rpc call context
@param r       result to add size.
@return an object that represents the last referenced block from this response.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/RSRpcServices.java