@Override
    public void start() {
        isStarted = true;
        resetLoopCount();
        if (isVisible) {
            startRunning();
        }
    }
Constructor for GifDrawable.

@see #setFrameTransformation(Transformation, Bitmap)

@param context A context.
@param bitmapProvider An {@link GifDecoder.BitmapProvider} that can be used to
                      retrieve re-usable {@link Bitmap}s.
@param bitmapPool A {@link BitmapPool} that can be used to return
                  the first frame when this drawable is recycled.
@param frameTransformation An {@link Transformation} that can be applied to each frame.
@param targetFrameWidth The desired width of the frames displayed by this drawable (the width of the view or
                        {@link com.bumptech.glide.request.target.Target} this drawable is being loaded into).
@param targetFrameHeight The desired height of the frames displayed by this drawable (the height of the view or
                         {@link com.bumptech.glide.request.target.Target} this drawable is being loaded into).
@param gifHeader The header data for this gif.
@param data The full bytes of the gif.
@param firstFrame The decoded and transformed first frame of this gif.
core/src/main/java/com/bumptech/glide/load/resource/gif/GifDrawable.java