Aura: Add --aura-laptop-mode to fill the workspace with a single window.

ui/aura_shell/root_window_layout_manager.h

 // Copyright (c) 2011 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_AURA_SHELL_ROOT_WINDOW_LAYOUT_MANAGER_H_
 #define UI_AURA_SHELL_ROOT_WINDOW_LAYOUT_MANAGER_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
@@ skipping 28 matching lines @@
   virtual void OnWindowAddedToLayout(aura::Window* child) OVERRIDE;
   virtual void OnWillRemoveWindowFromLayout(aura::Window* child) OVERRIDE;
   virtual void OnChildWindowVisibilityChanged(aura::Window* child,
                                               bool visible) OVERRIDE;
   virtual void SetChildBounds(aura::Window* child,
                               const gfx::Rect& requested_bounds) OVERRIDE;
 
  private:
   aura::Window* owner_;
 
+  // May be NULL if we're not painting a background.
   views::Widget* background_widget_;
 
   DISALLOW_COPY_AND_ASSIGN(RootWindowLayoutManager);
 };
 
 }  // namespace internal
 }  // namespace aura_shell
 
 #endif  // UI_AURA_SHELL_ROOT_WINDOW_LAYOUT_MANAGER_H_