private void initFixedOutputStream() throws IOException {
    if (shouldFixStream || mOutputStream == null) {
      return;
    }
    shouldFixStream = true;
    mInputStream.reset();
    copyFromIsToOs(mInputStream, mOutputStream, mCurrentOffset - 2);
    mInputStream.skip(2);
  }
@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