DevTools: properly update paint profiler upon new event being set

Source/devtools/front_end/timeline/TimelinePaintProfilerView.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.TracingTimelineFrameModel} frameModel
  * @extends {WebInspector.SplitWidget}
  */
 WebInspector.TimelinePaintProfilerView = function(frameModel)
@@ skipping 31 matching lines @@
      * @param {!WebInspector.Target} target
      * @param {!WebInspector.TracingModel.Event} event
      * @return {boolean}
      */
     setEvent: function(target, event)
     {
         this._disposeSnapshot();
         this._target = target;
         this._event = event;
 
-        this._updateWhenVisible = true;
+        if (this.isShowing())
+            this._update();
+        else
+            this._updateWhenVisible = true;
 
         if (this._event.name === WebInspector.TimelineModel.RecordType.Paint)
             return !!event.picture;
         if (this._event.name === WebInspector.TimelineModel.RecordType.RasterTask)
             return this._frameModel.hasRasterTile(this._event);
         return false;
     },
 
     _update: function()
     {
@@ skipping 134 matching lines @@
      * @param {?DOMAgent.Rect} maskRectangle
      */
     setMask: function(maskRectangle)
     {
         this._maskRectangle = maskRectangle;
         this._maskElement.classList.toggle("hidden", !maskRectangle);
     },
 
     __proto__: WebInspector.Widget.prototype
 };