return NS_OK;
head->mNext = new ContentListItem(aContent); if (! head->mNext) return NS_ERROR_OUT_OF_MEMORY;
    Add(nsIRDFResource* aResource, nsIContent* aContent)    {        NS_PRECONDITION(mResources != nsnull, "not initialized");        if (! mResources)            return NS_ERROR_NOT_INITIALIZED;        ContentListItem* head =            (ContentListItem*) PL_HashTableLookup(mResources, aResource);        if (! head) {            head = new ContentListItem(aContent);            if (! head)                return NS_ERROR_OUT_OF_MEMORY;            PL_HashTableAdd(mResources, aResource, head);        }        else {            while (1) {                if (head->mContent == aContent) {                    NS_ERROR("attempt to add same element twice");                    return NS_ERROR_ILLEGAL_VALUE;                }                if (! head->mNext)                    break;                head = head->mNext;            }            head->mNext = new ContentListItem(aContent);            if (! head->mNext)                return NS_ERROR_OUT_OF_MEMORY;        }        return NS_OK;    }