Devtools: Fix disabled element state pane button after reloading

Source/devtools/front_end/elements/ElementStatePaneWidget.js

 // Copyright (c) 2015 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
  * @extends {WebInspector.StylesSidebarPane.BaseToolbarPaneWidget}
  * @param {!WebInspector.ToolbarItem} toolbarItem
  */
 WebInspector.ElementStatePaneWidget = function(toolbarItem)
@@ skipping 74 matching lines @@
             this._updateInputs(node);
     },
 
     /**
      * @override
      * @param {?WebInspector.DOMNode} newNode
      */
     onNodeChanged: function(newNode)
     {
         this._updateTarget(newNode? newNode.target() : null);
-        this.toolbarItem().setEnabled(!!newNode);
-        if (!newNode) {
-            if (this.isShowing())
-                this.detach();
-            return;
-        }
-        this._updateInputs(newNode);
+        if (newNode)
+            this._updateInputs(newNode);
     },
 
     /**
      * @param {!WebInspector.DOMNode} node
      */
     _updateInputs: function(node)
     {
         var nodePseudoState = node.getUserProperty(WebInspector.CSSStyleModel.PseudoStatePropertyName) || [];
         var inputs = this._inputs;
         for (var i = 0; i < inputs.length; ++i) {
             inputs[i].disabled = !!node.pseudoType();
             inputs[i].checked = nodePseudoState.indexOf(inputs[i].state) >= 0;
         }
     },
 
     __proto__: WebInspector.StylesSidebarPane.BaseToolbarPaneWidget.prototype
 }
 
 /**
  * @constructor
  * @implements {WebInspector.ToolbarItem.Provider}
  */
 WebInspector.ElementStatePaneWidget.ButtonProvider = function()
 {
     this._button = new WebInspector.ToolbarButton(WebInspector.UIString("Toggle Element State"), "pin-toolbar-item");
     this._button.addEventListener("click", this._clicked, this);
     this._view = new WebInspector.ElementStatePaneWidget(this.item());
+    WebInspector.context.addFlavorChangeListener(WebInspector.DOMNode, this._nodeChanged, this);
+    this._nodeChanged();
 }
 
 WebInspector.ElementStatePaneWidget.ButtonProvider.prototype = {
     _clicked: function()
     {
         var stylesSidebarPane = WebInspector.ElementsPanel.instance().sidebarPanes.styles;
         stylesSidebarPane.showToolbarPane(!this._view.isShowing() ? this._view : null);
     },
 
     /**
      * @override
      * @return {!WebInspector.ToolbarItem}
      */
     item: function()
     {
         return this._button;
+    },
+
+    _nodeChanged: function()
+    {
+        var enabled = !!WebInspector.context.flavor(WebInspector.DOMNode);
+        this._button.setEnabled(enabled);
+        if (!enabled && this._button.toggled())
+            WebInspector.ElementsPanel.instance().sidebarPanes.styles.showToolbarPane(null);
     }
 }