if (mURL)
if (mURL != nsnull)
CSSStyleSheetImpl::Init(nsIURL* aURL){  NS_PRECONDITION(aURL, "null ptr");  if (! aURL)    return NS_ERROR_NULL_POINTER;  NS_ASSERTION(mURL == nsnull, "already initialized");  if (mURL)    return NS_ERROR_ALREADY_INITIALIZED;  mURL.SetAddRef(aURL);  return NS_OK;}