Revert 114095 - Move the concept of Activation to the Shell.

ui/aura/client/stacking_client.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_CLIENT_STACKING_CLIENT_H_
 #define UI_AURA_CLIENT_STACKING_CLIENT_H_
 #pragma once
 
 #include "ui/aura/aura_export.h"
 
 namespace aura {
 
 class Window;
 
 // An interface implemented by an object that stacks windows.
 class AURA_EXPORT StackingClient {
  public:
   virtual ~StackingClient() {}
 
   // Called by the Window when its parent is set to NULL. The delegate is given
   // an opportunity to inspect the window and add it to a default parent window
   // of its choosing.
   virtual void AddChildToDefaultParent(Window* window) = 0;
+
+  // Returns true if |window| can be activated or deactivated.
+  // A window manager typically defines some notion of "top level window" that
+  // supports activation/deactivation.
+  virtual bool CanActivateWindow(Window* window) const = 0;
+
+  // Returns the window that should be activated other than |ignore|.
+  virtual Window* GetTopmostWindowToActivate(Window* ignore) const = 0;
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_CLIENT_STACKING_CLIENT_H_