Add a container window to host the desktop window hierarchy in AURA.

ui/views/widget/desktop_aura/desktop_focus_rules.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 UI_VIEWS_WIDGET_DESKTOP_FOCUS_RULES_H_
 #define UI_VIEWS_WIDGET_DESKTOP_FOCUS_RULES_H_
 
 #include "ui/views/corewm/base_focus_rules.h"
 
 namespace views {
 
 class DesktopFocusRules : public corewm::BaseFocusRules {
  public:
-  DesktopFocusRules();
+  explicit DesktopFocusRules(aura::Window* content_window);
   virtual ~DesktopFocusRules();
 
  private:
   // Overridden from corewm::BaseFocusRules:
   virtual bool SupportsChildActivation(aura::Window* window) const OVERRIDE;
 
+  // The content window. This is an activatable window even though it is a
+  // child.
+  aura::Window* content_window_;
+
   DISALLOW_COPY_AND_ASSIGN(DesktopFocusRules);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_DESKTOP_FOCUS_RULES_H_