Fix zooming bug (#3715)

lib/timeline/Timeline.js

@@ -189,7 +189,7 @@ function Timeline (container, items, groups, options) {
   this.initialFitDone = false;
   this.on('changed', function (){
     if (me.itemsData == null) return;
-    if (!me.initialFitDone || !me.options.rollingMode) {
+    if (!me.initialFitDone && !me.options.rollingMode) {
       me.initialFitDone = true;
       if (me.options.start != undefined || me.options.end != undefined) {
         if (me.options.start == undefined || me.options.end == undefined) {
@@ -204,7 +204,8 @@ function Timeline (container, items, groups, options) {
       }
     }
 
-    if (!me.initialDrawDone && (me.initialRangeChangeDone || (!me.options.start && !me.options.end) || me.options.rollingMode)) {
+    if (!me.initialDrawDone && (me.initialRangeChangeDone || (!me.options.start && !me.options.end) 
+      || me.options.rollingMode)) {
       me.initialDrawDone = true;
       me.itemSet.initialDrawDone = true;
       me.dom.root.style.visibility = 'visible';