private void startRunning() {
        // If we have only a single frame, we don't want to decode it endlessly.
        if (decoder.getFrameCount() == 1) {
            invalidateSelf();
        }  else if (!isRunning) {
            isRunning = true;
            frameLoader.start();
            invalidateSelf();
        }
    }
Clears temporary data and resets the drawable back to the first frame.
core/src/main/java/com/bumptech/glide/load/resource/gif/GifDrawable.java