Set tree data just before render happens

lib/carto/renderer_js.js

@@ -279,14 +279,14 @@ CartoCSS.prototype = {
 
 carto.RendererJS = function (options) {
     this.options = options || {};
-    var reference = this.options.reference || require('./torque-reference').version.latest;
-    tree.Reference.setData(reference);
     this.options.mapnik_version = this.options.mapnik_version || 'latest';
+    this.reference = this.options.reference || require('./torque-reference').version.latest;
     this.options.strict = this.options.hasOwnProperty('strict') ? this.options.strict : false;
 };
 
 // Prepare a javascript object which contains the layers
 carto.RendererJS.prototype.render = function render(cartocss, callback) {
+    tree.Reference.setData(this.reference);
     return new CartoCSS(cartocss, this.options);
 }