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

third_party/WebKit/Source/devtools/front_end/ui/RootView.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
  * @extends {WebInspector.VBox}
  */
 WebInspector.RootView = function()
 {
     WebInspector.VBox.call(this);
     this.markAsRoot();
     this.element.classList.add("root-view");
     this.element.setAttribute("spellcheck", false);
 }
 
 WebInspector.RootView.prototype = {
     /**
      * @param {!Document} document
      */
     attachToDocument: function(document)
     {
         document.defaultView.addEventListener("resize", this.doResize.bind(this), false);
         this._window = document.defaultView;
         this.doResize();
-        this.show(document.body);
+        this.show(/** @type {!Element} */ (document.body));
     },
 
     doResize: function()
     {
         if (this._window) {
             var size = this.constraints().minimum;
             var zoom = WebInspector.zoomManager.zoomFactor();
             var right = Math.min(0, this._window.innerWidth - size.width / zoom);
             this.element.style.marginRight = right + "px";
             var bottom = Math.min(0, this._window.innerHeight - size.height / zoom);
             this.element.style.marginBottom = bottom + "px";
         }
         WebInspector.VBox.prototype.doResize.call(this);
     },
 
     __proto__: WebInspector.VBox.prototype
 }