const nsString& aMimeType)
const nsString& aMimeType, PRUint32 aFlags)
nsTextEncoder::Init(nsIPresShell* aPresShell, nsIDocument* aDocument,                    const nsString& aMimeType){  if (!aDocument)    return NS_ERROR_INVALID_ARG;  if (!aPresShell)    return NS_ERROR_INVALID_ARG;  mDocument = aDocument;  NS_ADDREF(mDocument);  mPresShell = aPresShell;  NS_ADDREF(aPresShell);  mMimeType = aMimeType;  return NS_OK;}