DevTools: Refactor network panel overview

Source/devtools/front_end/ui_lazy/TimelineGrid.js

 /*
  * Copyright (C) 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2008, 2009 Anthony Ricaud <rik@webkit.org>
  * Copyright (C) 2009 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
@@ skipping 21 matching lines @@
  * @constructor
  */
 WebInspector.TimelineGrid = function()
 {
     this.element = createElement("div");
     this.element.appendChild(WebInspector.Widget.createStyleElement("ui_lazy/timelineGrid.css"));
 
     this._dividersElement = this.element.createChild("div", "resources-dividers");
 
     this._gridHeaderElement = createElement("div");
-    this._gridHeaderElement.id = "timeline-grid-header";
+    this._gridHeaderElement.classList.add("timeline-grid-header");
     this._eventDividersElement = this._gridHeaderElement.createChild("div", "resources-event-dividers");
     this._dividersLabelBarElement = this._gridHeaderElement.createChild("div", "resources-dividers-label-bar");
     this.element.appendChild(this._gridHeaderElement);
 
     this._leftCurtainElement = this.element.createChild("div", "timeline-cpu-curtain-left");
     this._rightCurtainElement = this.element.createChild("div", "timeline-cpu-curtain-right");
 }
 
 /**
  * @param {!WebInspector.TimelineGrid.Calculator} calculator
@@ skipping 277 matching lines @@
 
     /** @return {number} */
     zeroTime: function() { },
 
     /** @return {number} */
     maximumBoundary: function() { },
 
     /** @return {number} */
     boundarySpan: function() { }
 }