DevTools: rely upon shouldHideOnDetach when considering re-layout of elements and sources panels.

Source/devtools/front_end/extensions/ExtensionPanel.js

 /*
  * Copyright (C) 2012 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 173 matching lines @@
  * @constructor
  * @extends {WebInspector.SidebarPane}
  * @param {!WebInspector.ExtensionServer} server
  * @param {string} panelName
  * @param {string} title
  * @param {string} id
  */
 WebInspector.ExtensionSidebarPane = function(server, panelName, title, id)
 {
     WebInspector.SidebarPane.call(this, title);
-    this.setHideOnDetach();
     this._panelName = panelName;
     this._server = server;
     this._id = id;
 }
 
 WebInspector.ExtensionSidebarPane.prototype = {
     /**
      * @return {string}
      */
     id: function()
@@ skipping 104 matching lines @@
         if (!title)
             section.titleLessMode();
         section.expand();
         section.editable = false;
         this._objectPropertiesView.element.appendChild(section.element);
         callback();
     },
 
     __proto__: WebInspector.SidebarPane.prototype
 }