if (interval != -1)
if (interval >= 0)
nsIncrementalDownload::Init(nsIURI *uri, nsIFile *dest,                            PRInt32 chunkSize, PRInt32 interval){  // Keep it simple: only allow initialization once  NS_ENSURE_FALSE(mURI, NS_ERROR_ALREADY_INITIALIZED);  mDest = do_QueryInterface(dest);  NS_ENSURE_ARG(mDest);  mURI = uri;  mFinalURI = uri;  if (chunkSize != -1)    mChunkSize = chunkSize;  if (interval != -1)    mInterval = interval;  return NS_OK;}