MOZ_COUNT_CTOR(UndisplayedMap);
UndisplayedMap::UndisplayedMap(PRUint32 aNumBuckets){  mTable = PL_NewHashTable(aNumBuckets, (PLHashFunction)HashKey,                           (PLHashComparator)CompareKeys,                           (PLHashComparator)nsnull,                           nsnull, nsnull);  mLastLookup = nsnull;}