async updateSource(mediaStreamSource) {
    if (this.source_) {
      this.abortController_.abort();
      this.abortController_ = new AbortController();
      this.source_.destroy();
      this.processedStream_ = null;
    }
    this.source_ = mediaStreamSource;
    this.source_.setDebugPath('debug.pipeline.source_');
    console.log(
        '[Pipeline] Updated source.',
        'debug.pipeline.source_ = ', this.source_);
    await this.maybeStartPipeline_();
  }
Sets a new source for the pipeline.
@param {!MediaStreamSource} mediaStreamSource