--- a/dom/system/IOUtils.h
+++ b/dom/system/IOUtils.h
@@ -215,30 +215,16 @@ class IOUtils final {
    * @return The number of bytes written to the file, or an error if the write
    *         failed or was incomplete.
    */
   static Result<uint32_t, IOError> WriteUTF8Sync(
       nsIFile* aFile, const nsCString& aUTF8String,
       const InternalWriteOpts& aOptions);
 
   /**
-   * Attempts to write |aBytes| to the file pointed by |aFd|.
-   *
-   * @param aFd    An open PRFileDesc for the destination file to be
-   *               overwritten.
-   * @param aFile  The location of the file.
-   * @param aBytes The data to write to the file.
-   *
-   * @return The number of bytes written to the file, or an error if the write
-   *         failed or was incomplete.
-   */
-  static Result<uint32_t, IOError> WriteSync(PRFileDesc* aFd, nsIFile* aFile,
-                                             const Span<const uint8_t>& aBytes);
-
-  /**
    * Attempts to move the file located at |aSourceFile| to |aDestFile|.
    *
    * @param aSourceFile  The location of the file to move.
    * @param aDestFile    The destination for the file.
    * @param noOverWrite If true, abort with an error if a file already exists at
    *                    |aDestFile|. Otherwise, the file will be overwritten by
    *                    the move.
    *