async parseImages_(imageTags, iFrameTags) {
    // Create image stream for each image tag.
    const imageStreamPromises = imageTags.map(async (tag) => {
      const disableThumbnails = this.config_.disableThumbnails;
      if (disableThumbnails) {
        return null;
      }
      try {
        const streamInfo = await this.createStreamInfoFromImageTag_(tag);
        return streamInfo.stream;
      } catch (e) {
        if (this.config_.hls.ignoreImageStreamFailures) {
          return null;
        }
        throw e;
      }
    }).concat(iFrameTags.map((tag) => {
      const disableThumbnails = this.config_.disableThumbnails;
      if (disableThumbnails) {
        return null;
      }
      try {
        const streamInfo = this.createStreamInfoFromIframeTag_(tag);
        const ContentType = shaka.util.ManifestParserUtils.ContentType;
        if (streamInfo.stream.type !== ContentType.IMAGE) {
          return null;
        }
        return streamInfo.stream;
      } catch (e) {
        if (this.config_.hls.ignoreImageStreamFailures) {
          return null;
        }
        throw e;
      }
    }));
    const imageStreams = await Promise.all(imageStreamPromises);
    return imageStreams.filter((s) => s);
  }
@param {!Array<!shaka.hls.Tag>} imageTags from the playlist.
@param {!Array<!shaka.hls.Tag>} iFrameTags from the playlist.
@return {!Promise<!Array<!shaka.extern.Stream>>}
@private