Devtools: Fix disabled element state pane button after reloading

Source/devtools/front_end/elements/StylesSidebarPane.js

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * 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
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 24 matching lines @@
 WebInspector.StylesSidebarPane = function(requestShowCallback)
 {
     WebInspector.ElementsSidebarPane.call(this, WebInspector.UIString("Styles"));
 
     this.element.addEventListener("contextmenu", this._contextMenuEventFired.bind(this), true);
     WebInspector.moduleSetting("colorFormat").addChangeListener(this.update.bind(this));
     WebInspector.moduleSetting("textEditorIndent").addChangeListener(this.update.bind(this));
 
     var toolbar = new WebInspector.ExtensibleToolbar("styles-sidebarpane-toolbar", this.element);
     toolbar.element.classList.add("styles-pane-toolbar");
+    this._currentToolbarPane = null;
 
     this._requestShowCallback = requestShowCallback;
     var toolbarPaneContainer = this.element.createChild("div", "styles-sidebar-toolbar-pane-container");
     this._toolbarPaneElement = toolbarPaneContainer.createChild("div", "styles-sidebar-toolbar-pane");
     this._sectionsContainer = this.element.createChild("div");
 
     this._stylesPopoverHelper = new WebInspector.StylesPopoverHelper();
 
     this._linkifier = new WebInspector.Linkifier(new WebInspector.Linkifier.DefaultCSSFormatter());
 
@@ skipping 3130 matching lines @@
  * @param {!WebInspector.ToolbarItem} toolbarItem
  */
 WebInspector.StylesSidebarPane.BaseToolbarPaneWidget = function(toolbarItem)
 {
     WebInspector.Widget.call(this);
     this._toolbarItem = toolbarItem;
     WebInspector.context.addFlavorChangeListener(WebInspector.DOMNode, this._nodeChanged, this);
 }
 
 WebInspector.StylesSidebarPane.BaseToolbarPaneWidget.prototype = {
-    /**
-     * @return {!WebInspector.ToolbarItem}
-     */
-    toolbarItem: function()
-    {
-        return this._toolbarItem;
-    },
-
     _nodeChanged: function()
     {
         if (!this.isShowing())
             return;
 
         var elementNode = WebInspector.SharedSidebarModel.elementNode(WebInspector.context.flavor(WebInspector.DOMNode));
         this.onNodeChanged(elementNode);
     },
 
     /**
@@ skipping 48 matching lines @@
 
     /**
      * @override
      * @return {?WebInspector.ToolbarItem}
      */
     item: function()
     {
         return this._button;
     }
 }