code: function update() {
      // TODO(sorvell): instead the root should always be enqueued to helps record that it is dirty.
      // Then, in `render`, the top most (in the distribution tree) "dirty" root should be rendered.
      var distributionRoot = this._findDistributionRoot(this.host);
      //console.log('update from', this.host, 'root', distributionRoot.host, distributionRoot._clean);
      if (distributionRoot._clean) {
        distributionRoot._clean = false;
        enqueue(function() {
          distributionRoot.render();
        });
      }
    }
docs: async render the "top" distributor (this is all that is needed to distribute this host).