check parent DOM elements for direction attribute (#2237)

* Fix PR comment
* Remove extra line

lib/timeline/Timeline.js

@@ -63,7 +63,12 @@ function Timeline (container, items, groups, options) {
   this._create(container);
 
   if (!options || (options && typeof options.rtl == "undefined")) {
-    this.options.rtl = window.getComputedStyle(this.dom.root, null).direction == "rtl";
+    var directionFromDom, domNode = this.dom.root;
+    while (!directionFromDom && domNode) {
+      directionFromDom = window.getComputedStyle(domNode, null).direction;
+      domNode = domNode.parentElement;
+    }
+    this.options.rtl = (directionFromDom && (directionFromDom.toLowerCase() == "rtl"));
   } else {
     this.options.rtl = options.rtl;
   }