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

Source/devtools/front_end/sources/SourcesPanel.js

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2011 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:
  * 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 1124 matching lines @@
         if (position === "right")
             vertically = false;
         else if (position === "bottom")
             vertically = true;
         else
             vertically = WebInspector.inspectorView.element.offsetWidth < 680;
 
         if (this.sidebarPaneView && vertically === !this._splitWidget.isVertical())
             return;
 
+        if (this.sidebarPaneView && this.sidebarPaneView.shouldHideOnDetach())
+            return; // We can't reparent extension iframes.
+
         if (this.sidebarPaneView)
             this.sidebarPaneView.detach();
 
         this._splitWidget.setVertical(!vertically);
         this._splitWidget.element.classList.toggle("sources-split-view-vertical", vertically);
 
         if (!vertically)
             this._splitWidget.uninstallResizer(this._sourcesView.toolbarContainerElement());
         else
             this._splitWidget.installResizer(this._sourcesView.toolbarContainerElement());
@@ skipping 68 matching lines @@
     {
         var pane = /** @type {!WebInspector.ExtensionSidebarPane} */ (event.data);
         this._addExtensionSidebarPane(pane);
     },
 
     /**
      * @param {!WebInspector.ExtensionSidebarPane} pane
      */
     _addExtensionSidebarPane: function(pane)
     {
-        if (pane.panelName() === this.name) {
-            this.setHideOnDetach();
+        if (pane.panelName() === this.name)
             this._extensionSidebarPanesContainer.addPane(pane);
-        }
     },
 
     /**
      * @return {!WebInspector.SourcesView}
      */
     sourcesView: function()
     {
         return this._sourcesView;
     },
 
@@ skipping 216 matching lines @@
 WebInspector.SourcesPanelFactory.prototype = {
     /**
      * @override
      * @return {!WebInspector.Panel}
      */
     createPanel: function()
     {
         return WebInspector.SourcesPanel.instance();
     }
 }