mDB->AddListener(this);
nsMsgDBThreadEnumerator::nsMsgDBThreadEnumerator(nsMsgDatabase* db,                                     nsMsgDBThreadEnumeratorFilter filter)    : mDB(db), mTableCursor(nsnull), mResultThread(nsnull), mDone(PR_FALSE),      mFilter(filter){    NS_ADDREF(mDB);    mNextPrefetched = PR_FALSE;}