Timeline: fix frame offsets in Timeline details

third_party/WebKit/Source/devtools/front_end/timeline_model/TimelineFrameModel.js

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 226 matching lines @@
   }
 
   /**
    * @param {?SDK.Target} target
    * @param {!Array.<!SDK.TracingModel.Event>} events
    * @param {string} sessionId
    */
   addTraceEvents(target, events, sessionId) {
     this._target = target;
     this._sessionId = sessionId;
-    if (!events.length)
-      return;
-    if (events[0].startTime < this._minimumRecordTime)
-      this._minimumRecordTime = events[0].startTime;
     for (var i = 0; i < events.length; ++i)
       this._addTraceEvent(events[i]);
   }
 
   /**
    * @param {!SDK.TracingModel.Event} event
    */
   _addTraceEvent(event) {
     var eventNames = TimelineModel.TimelineModel.RecordType;
+    if (event.startTime && event.startTime < this._minimumRecordTime)
+      this._minimumRecordTime = event.startTime;
 
     if (event.name === eventNames.SetLayerTreeId) {
       var sessionId = event.args['sessionId'] || event.args['data']['sessionId'];
       if (this._sessionId === sessionId)
         this._layerTreeId = event.args['layerTreeId'] || event.args['data']['layerTreeId'];
     } else if (event.name === eventNames.TracingStartedInPage) {
       this._mainThread = event.thread;
     } else if (
         event.phase === SDK.TracingModel.Phase.SnapshotObject && event.name === eventNames.LayerTreeHostImplSnapshot &&
         parseInt(event.id, 0) === this._layerTreeId) {
@@ skipping 256 matching lines @@
   constructor(triggerTime, timeByCategory) {
     /** @type {!Object.<string, number>} */
     this.timeByCategory = timeByCategory;
     /** @type {!Array.<!TimelineModel.LayerPaintEvent>} */
     this.paints = [];
     /** @type {number|undefined} */
     this.mainFrameId = undefined;
     this.triggerTime = triggerTime;
   }
 };