docs: public boolean isCompleteAt(int length) {
      if (mImageFormat != DefaultImageFormats.JPEG) {
        return true;
      }
      // If the image is backed by FileInputStreams return true since they will always be complete.
      if (mInputStreamSupplier != null) {
        return true;
      }
      // The image should be backed by a ByteBuffer
      Preconditions.checkNotNull(mPooledByteBufferRef);
      PooledByteBuffer buf = mPooledByteBufferRef.get();
      return (buf.read(length - 2) == (byte) JfifUtil.MARKER_FIRST_BYTE)
          && (buf.read(length - 1) == (byte) JfifUtil.MARKER_EOI);
    }