static createManifest(originalUri) {
    return {
      creationTime: Date.now(),
      appMetadata: null,
      drmInfo: null,
      duration: 90,
      expiration: Infinity,
      originalManifestUri: originalUri,
      streams: [],
      sessionIds: [],
      size: 1024,
      sequenceMode: false,
    };
  }
@param {string} originalUri
@return {shaka.extern.ManifestDB}