dispatchFetch_(reference, stream, streamDataCallback, isPreload = false) {
    goog.asserts.assert(
        this.playerInterface_.netEngine, 'Must have net engine');
    return shaka.media.StreamingEngine.dispatchFetch(
        reference, stream, streamDataCallback || null,
        this.config_.retryParameters, this.playerInterface_.netEngine);
  }
Fetches the given segment.

@param {(!shaka.media.InitSegmentReference|
         !shaka.media.SegmentReference)} reference
@param {!shaka.extern.Stream} stream
@param {?function(BufferSource):!Promise=} streamDataCallback
@param {boolean=} isPreload

@return {!shaka.net.NetworkingEngine.PendingRequest}
@private