HistoryKey(PRUint32 aKey) { itsHash = aKey;
HistoryKey(PRUint32 aContentID, nsIStatefulFrame::StateType aStateType) { MOZ_COUNT_CTOR(HistoryKey); itsHash = aContentID * nsIStatefulFrame::eNumStateTypes + aStateType;
   HistoryKey(PRUint32 aKey) {     itsHash = aKey;   }