In Windows 8 chrome metro mode if we Alt tabbed away from chrome while a tab was loading, we would …

content/browser/renderer_host/render_widget_host_view_win.h

 // Copyright (c) 2012 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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_WIN_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_WIN_H_
 #pragma once
 
 #include <atlbase.h>
 #include <atlapp.h>
@@ skipping 458 matching lines @@
   // The tooltip control hwnd
   HWND tooltip_hwnd_;
   // Whether or not a tooltip is currently visible. We use this to track
   // whether or not we want to force-close the tooltip when we receive mouse
   // move notifications from the renderer. See comment in OnMsgSetTooltipText.
   bool tooltip_showing_;
 
   // Factory used to safely scope delayed calls to ShutdownHost().
   base::WeakPtrFactory<RenderWidgetHostViewWin> weak_factory_;
 
-  // Our parent HWND.  We keep a reference to it as we SetParent(NULL) when
-  // hidden to prevent getting messages (Paint, Resize...), and we reattach
-  // when shown again.
-  HWND parent_hwnd_;
-
   // The time at which this view started displaying white pixels as a result of
   // not having anything to paint (empty backing store from renderer). This
   // value returns true for is_null() if we are not recording whiteout times.
   base::TimeTicks whiteout_start_time_;
 
   // The time it took after this view was selected for it to be fully painted.
   base::TimeTicks web_contents_switch_paint_time_;
 
   // Registrar so we can listen to RENDERER_PROCESS_TERMINATED events.
   content::NotificationRegistrar registrar_;
@@ skipping 62 matching lines @@
 
   // Are touch events currently enabled?
   bool touch_events_enabled_;
 
   scoped_ptr<ui::GestureRecognizer> gesture_recognizer_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewWin);
 };
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_WIN_H_