async updateSink(mediaStreamSink) {
    if (this.sink_) this.sink_.destroy();
    this.sink_ = mediaStreamSink;
    console.log(
        '[Pipeline] Updated sink.', 'debug.pipeline.sink_ = ', this.sink_);
    if (this.processedStream_) {
      await this.sink_.setMediaStream(this.processedStream_);
    } else {
      await this.maybeStartPipeline_();
    }
  }
Sets a new sink for the pipeline.
@param {!MediaStreamSink} mediaStreamSink