NS_ENSURE_TRUE(mPresShell, NS_ERROR_NOT_AVAILABLE);
if (!mPresShell) return;
FrameManager::SetUndisplayedContent(nsIContent* aContent,                                     nsIStyleContext* aStyleContext){  NS_ENSURE_TRUE(mPresShell, NS_ERROR_NOT_AVAILABLE);  #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) {    nsresult result = NS_OK;    nsIContent* parent = nsnull;    aContent->GetParent(parent);    NS_ASSERTION(parent, "undisplayed content must have a parent");    if (parent) {      result = mUndisplayedMap->AddNodeFor(parent, aContent, aStyleContext);      NS_RELEASE(parent);    }    return result;  }  return NS_ERROR_OUT_OF_MEMORY;}