DevTools: keep widgets in widget hierarchy upon hide, split attach/detach cycle from show/hide.

third_party/WebKit/Source/devtools/front_end/ui/SidebarPane.js

 /*
  * Copyright (C) 2007 Apple 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
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 28 matching lines @@
     this.element.textContent = pane.title();
     this.element.tabIndex = 0;
     this.element.addEventListener("click", this._toggleExpanded.bind(this), false);
     this.element.addEventListener("keydown", this._onTitleKeyDown.bind(this), false);
 }
 
 WebInspector.SidebarPaneTitle.prototype = {
     _expand: function()
     {
         this.element.classList.add("expanded");
-        this._pane.show(this.element.parentElement, /** @type {?Element} */ (this.element.nextSibling));
+        this._pane.show(/** @type {!Element} */(this.element.parentElement), /** @type {?Element} */ (this.element.nextSibling));
     },
 
     _collapse: function()
     {
         this.element.classList.remove("expanded");
         if (this._pane.element.parentNode === this.element.parentNode)
             this._pane.detach();
     },
 
     _toggleExpanded: function()
@@ skipping 103 matching lines @@
             if (!this.hasTab(title))
                 this.appendTab(title, title, pane);
         } else {
             if (this.hasTab(title))
                 this.closeTab(title);
         }
     },
 
     __proto__: WebInspector.TabbedPane.prototype
 }