if (!aContent) return NS_ERROR_NULL_POINTER;
NS_ENSURE_ARG_POINTER(aContent);
FrameManager::GetUndisplayedContent(nsIContent* aContent, nsIStyleContext** aResult){  if (!aContent)    return NS_ERROR_NULL_POINTER;  *aResult = nsnull;  // initialize out param  if (mUndisplayedMap)    mUndisplayedMap->GetNodeFor(aContent, aResult);      return NS_OK;}