nsresult rv = NS_OK; PRInt32  prevIndex = 0;
nsSessionHistory::GoForward(nsIWebShell * aPrev){   nsresult rv = NS_OK;   PRInt32  prevIndex = 0;   if (mHistoryCurrentIndex == mHistoryLength-1)      return NS_ERROR_FAILURE;   Goto((mHistoryCurrentIndex+1), aPrev, PR_FALSE);   return NS_OK;}