List.add('rect-track');this.asyncStyle_=false;this.rects_=null;this.heading_=document.createElement('tr-ui-b-heading');Polymer.dom(this).appendChild(this.heading_);},set heading(heading){this.heading_.heading=heading;},get heading(){return this.heading_.heading;},set tooltip(tooltip){this.heading_.tooltip=tooltip;},set selectionGenerator(generator){this.heading_.selectionGenerator=generator;},set expanded(expanded){this.heading_.expanded=!!expanded;},set arrowVisible(arrowVisible){this.heading_....