getResolutionList_(variants) {
    const resolutions = [];
    for (const variant of variants) {
      const video = variant.video;
      if (!video || !video.height || !video.width) {
        continue;
      }
      resolutions.push({
        height: video.height,
        width: video.width,
      });
    }

    return resolutions.sort((v1, v2) => {
      return v1.width - v2.width;
    });
  }
@param {!Array<shaka.extern.Variant>} variants
@return {!Array<{height: number, width: number}>}
@private