toArray() {
    return [
      this.getAddonTemplates(),
      this.getStyles(),
      this.getTests(),
      this.getExternalTree(),
      this.getPublic(),
      this.getAppJavascript(),
    ].filter(Boolean);
  }
Returns an array of trees for this application

    @private
    @method toArray
    @return {Array} An array of trees