[cros Aura] Added modal container for screen lock.

ui/aura_shell/stacking_controller.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_STACKING_CONTROLLER_H_
 #define UI_AURA_SHELL_STACKING_CONTROLLER_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
@@ skipping 17 matching lines @@
   // activation.
   static aura::Window* GetActivatableWindow(aura::Window* window);
 
   // Overridden from aura::StackingClient:
   virtual void AddChildToDefaultParent(aura::Window* window) OVERRIDE;
   virtual bool CanActivateWindow(aura::Window* window) const OVERRIDE;
   virtual aura::Window* GetTopmostWindowToActivate(
       aura::Window* ignore) const OVERRIDE;
 
  private:
+  // Returns corresponding modal container for a modal window.
+  // If screen lock is not active, all modal windows are placed into the
+  // normal modal container.
+  // Otherwise those that originate from LockScreen container and above are
+  // placed in the screen lock modal container.
+  aura::Window* GetModalContainer(aura::Window* window) const;
+
   scoped_ptr<internal::AlwaysOnTopController> always_on_top_controller_;
 
   DISALLOW_COPY_AND_ASSIGN(StackingController);
 };
 
 }  // namespace internal
 }  // namespace aura_shell
 
 #endif  // UI_AURA_SHELL_STACKING_CONTROLLER_H_