public void deleteChangedReaderObserver(ChangedReadersObserver o) {
    // We don't check if observer present; it may not be (legitimately)
    this.changedReaderObservers.remove(o);
  }
@param o Observer no longer interested in changes in set of Readers.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HStore.java