NS_PRECONDITION(nsnull != aFirstChild, "null OUT parameter pointer"); if (nsnull == aListName) { *aFirstChild = (nsnull != mLines) ? mLines->mFirstChild : nsnull; return NS_OK; } else if (aListName == nsLayoutAtoms::floaterList) { *aFirstChild = mFloaters.FirstChild(); return NS_OK; } else if (aListName == nsLayoutAtoms::bulletList) { if (HaveOutsideBullet()) { *aFirstChild = mBullet; } else { *aFirstChild = nsnull; } return NS_OK; } *aFirstChild = nsnull; return NS_ERROR_INVALID_ARG;
aFirstChild = (nsnull != mLines) ? mLines->mFirstChild : nsnull; return NS_OK;
nsBlockFrame::FirstChild(nsIAtom* aListName, nsIFrame** aFirstChild) const{  NS_PRECONDITION(nsnull != aFirstChild, "null OUT parameter pointer");  if (nsnull == aListName) {    *aFirstChild = (nsnull != mLines) ? mLines->mFirstChild : nsnull;    return NS_OK;  }  else if (aListName == nsLayoutAtoms::floaterList) {    *aFirstChild = mFloaters.FirstChild();    return NS_OK;  }  else if (aListName == nsLayoutAtoms::bulletList) {    if (HaveOutsideBullet()) {      *aFirstChild = mBullet;    }    else {      *aFirstChild = nsnull;    }    return NS_OK;  }  *aFirstChild = nsnull;  return NS_ERROR_INVALID_ARG;}