Also

- The members: m_originClean, m_premultiplyAlpha and m_forciblyPremultiplyAlpha of ImageBitmap can be replaced by ImageBuffer::SerializationState. This will eliminate the need to sync the members of ImageBitmap and ImageBuffer::SerializationState. Also the whole struct can be copied in many places from std::pair<std::unique_ptr<ImageBuffer>, ImageBuffer::SerializationState> to ImageBitmap and vice versa.

Another approach is to make SerializationState enum class type and have an OptionSet< SerializationState> be stored in ImageBitmap:

enum class SerializationState {
    OriginClean = 1 << 0,
    PremultiplyAlpha = 1 << 1,
    ForciblyPremultiplyAlpha = 1 << 2,
};


class ImageBitmap {
public:
    bool originClean() const { return m_serializationState.contains(SerializationState::OriginClean); }

private:
    OptionSet<SerializationState> m_serializationState;
};

<rdar://problem/67105644>