requestManifest_(uris, isPlaylist) {
    const requestType = shaka.net.NetworkingEngine.RequestType.MANIFEST;

    const request = shaka.net.NetworkingEngine.makeRequest(
        uris, this.config_.retryParameters);

    const type = isPlaylist ?
        shaka.net.NetworkingEngine.AdvancedRequestType.MEDIA_PLAYLIST :
        shaka.net.NetworkingEngine.AdvancedRequestType.MASTER_PLAYLIST;
    return this.makeNetworkRequest_(request, requestType, {type});
  }
Makes a network request for the manifest and returns a Promise
with the resulting data.

@param {!Array<string>} uris
@param {boolean=} isPlaylist
@return {!shaka.net.NetworkingEngine.PendingRequest}
@private