handleDeferredCloseSegmentIndexes_(mediaState) {
    for (const [key, value] of this.deferredCloseSegmentIndex_.entries()) {
      const streamId = /** @type {string} */ (key);
      const closeSegmentIndex = /** @type {!function()} */ (value);
      if (streamId.includes(mediaState.type)) {
        closeSegmentIndex();
        this.deferredCloseSegmentIndex_.delete(streamId);
      }
    }
  }
Handles deferred releases of old SegmentIndexes for the mediaState's
content type from a previous update.
@param {!shaka.media.StreamingEngine.MediaState_} mediaState
@private