public AnimatedImageResultBuilder setPreviewBitmap(
      @Nullable CloseableReference<Bitmap> previewBitmap) {
    mPreviewBitmap = CloseableReference.cloneOrNull(previewBitmap);
    return this;
  }
Sets a preview bitmap.

@param previewBitmap the preview. The method clones the reference.
@return this builder
animated-base/src/main/java/com/facebook/imagepipeline/animated/base/AnimatedImageResultBuilder.java