Make sure WindowObservers are removed from window before destruction

ui/views/controls/native/native_view_host_aura.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/controls/native/native_view_host_aura.h"
 
 #include "base/logging.h"
 #include "ui/aura/client/focus_client.h"
 #include "ui/aura/window.h"
 #include "ui/views/controls/native/native_view_host.h"
@@ skipping 85 matching lines @@
     client->FocusWindow(window);
 }
 
 gfx::NativeViewAccessible NativeViewHostAura::GetNativeViewAccessible() {
   return NULL;
 }
 
 void NativeViewHostAura::OnWindowDestroyed(aura::Window* window) {
   DCHECK(window == host_->native_view());
   host_->NativeViewDestroyed();
+  aura::WindowObserver::OnWindowDestroyed(window);
 }
 
 // static
 NativeViewHostWrapper* NativeViewHostWrapper::CreateWrapper(
     NativeViewHost* host) {
   return new NativeViewHostAura(host);
 }
 
 }  // namespace views