void * state = nsnull; state = mStates.Remove(&key);
mStates.Remove(&key);
nsLayoutHistoryState::RemoveState(PRUint32 aContentID,                                                                  nsIStatefulFrame::StateType aStateType){  nsresult rv = NS_OK;  HistoryKey key(aContentID, aStateType);  void * state = nsnull;  state = mStates.Remove(&key);  return rv;}