@Nullable
  @Override
  public DrillDownInfo drillDown(Record selectedRecord) {
    // do nothing
    return null;
  }
Form new record list with records formed by only fields provided through fieldInfo and add a
count field for each record with value 1 We are doing two operation of selecting and adding new
field because of saving some CPU cycles on rebuilding the record again
@param fieldInfos List of FieldInfos required in the record
@param records    List of records which needs to be processed
@param countField Field which needs to be added with value 1 for each record
@return records after selecting required fields and adding count field
hbase-hbtop/src/main/java/org/apache/hadoop/hbase/hbtop/mode/RegionModeStrategy.java