Verifies WindowClosing() is invoked only once when a window is

ui/views/widget/desktop_aura/desktop_root_window_host_linux.cc

 // 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.
 
 #include "ui/views/widget/desktop_aura/desktop_root_window_host_linux.h"
 
 #include <X11/extensions/XInput2.h>
 #include <X11/Xatom.h>
 #include <X11/Xutil.h>
 
@@ skipping 319 matching lines @@
     MessageLoop::current()->PostTask(
         FROM_HERE,
         base::Bind(&DesktopRootWindowHostLinux::CloseNow,
                    close_widget_factory_.GetWeakPtr()));
   }
 }
 
 void DesktopRootWindowHostLinux::CloseNow() {
   if (xwindow_ == None)
     return;
+
+  native_widget_delegate_->OnNativeWidgetDestroying();
+
   // Remove the event listeners we've installed. We need to remove these
   // because otherwise we get assert during ~RootWindow().
   desktop_native_widget_aura_->root_window_event_filter()->RemoveHandler(
       x11_window_event_filter_.get());
 
   // Actually free our native resources.
   base::MessagePumpAuraX11::Current()->RemoveDispatcherForWindow(xwindow_);
   XDestroyWindow(xdisplay_, xwindow_);
   xwindow_ = None;
 
@@ skipping 743 matching lines @@
 DesktopRootWindowHost* DesktopRootWindowHost::Create(
     internal::NativeWidgetDelegate* native_widget_delegate,
     DesktopNativeWidgetAura* desktop_native_widget_aura,
     const gfx::Rect& initial_bounds) {
   return new DesktopRootWindowHostLinux(native_widget_delegate,
                                         desktop_native_widget_aura,
                                         initial_bounds);
 }
 
 }  // namespace views