private void skipAndWriteBytes(int length) throws IOException {
    if (shouldFixStream) {
      // NULLSAFE_FIXME[Parameter Not Nullable]
      copyFromIsToOs(mInputStream, mOutputStream, length);
    } else {
      mInputStream.skip(length);
    }
    mCurrentOffset += length;
  }
@param is InputStream to decode
@param os OutputStream to write fixed version of gif, if needed. (optional)
animated-gif-lite/src/main/java/com/facebook/animated/giflite/decoder/GifMetadataDecoder.java