@Override
  protected long getLogFileSize0() {
    T log = this.wal;
    return log == null ? 0 : log.getLogFileSize();
  }
iff the given WALFactory is using the DefaultWALProvider for meta and/or non-meta, count the
size of files (only rolled). if either of them aren't, count 0 for that provider.
hbase-server/src/main/java/org/apache/hadoop/hbase/wal/AbstractFSWALProvider.java