nsIContent* parent = nsnull; aContent->GetParent(parent);
nsCOMPtr<nsIContent> parent; aContent->GetParent(getter_AddRefs(parent));
FrameManager::SetUndisplayedContent(nsIContent* aContent,                                     nsStyleContext* aStyleContext){  if (!mPresShell)    return;  #ifdef DEBUG_UNDISPLAYED_MAP   static int i = 0;   printf("SetUndisplayedContent(%d): p=%p \n", i++, (void *)aContent);#endif  if (! mUndisplayedMap) {    mUndisplayedMap = new UndisplayedMap;  }  if (mUndisplayedMap) {    nsIContent* parent = nsnull;    aContent->GetParent(parent);    NS_ASSERTION(parent, "undisplayed content must have a parent");    if (parent) {      mUndisplayedMap->AddNodeFor(parent, aContent, aStyleContext);      NS_RELEASE(parent);    }  }}