DevTools: Make target on TimelineRecord nullable

Source/devtools/front_end/timeline/TracingTimelineModel.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @constructor
  * @param {!WebInspector.TracingModel} tracingModel
  * @param {!WebInspector.TimelineModel.Filter} recordFilter
  * @extends {WebInspector.TimelineModel}
  */
@@ skipping 588 matching lines @@
     /**
      * @return {?WebInspector.TimelineModel.Record}
      */
     initiator: function()
     {
         var initiator = this._event.initiator;
         return initiator ? initiator._timelineRecord : null;
     },
 
     /**
-     * @return {!WebInspector.Target}
+     * @return {?WebInspector.Target}
      */
     target: function()
     {
-        //FIXME: get it from this._event
-        return WebInspector.targetManager.targets()[0];
+        return this._event.thread.target();
     },
 
     /**
      * @return {number}
      */
     selfTime: function()
     {
         return this._event.selfTime;
     },
 
@@ skipping 130 matching lines @@
     },
 
     /**
      * @return {!WebInspector.TimelineModel}
      */
     timelineModel: function()
     {
         return this._model;
     }
 }