static preferredWidthHeightForSizePower(sizePower) {
        let w = 1 << Math.ceil(sizePower / 2);
        let h = 1 << Math.floor(sizePower / 2);
        if (w === 2 && h === 2) {
            w = 4;
            h = 1;
        }
        return {w, h};
    }
@param {!int} sizePower
@returns {{w: !int, h: !int}}