aura-mus: Implement DesktopWindowTreeHostMus::StackAbove().

services/ui/ws/access_policy.h

 // Copyright 2014 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 SERVICES_UI_WS_ACCESS_POLICY_H_
 #define SERVICES_UI_WS_ACCESS_POLICY_H_
 
 #include <stdint.h>
 
 #include "services/ui/public/interfaces/mus_constants.mojom.h"
@@ skipping 42 matching lines @@
       const ServerWindow* window) const = 0;
   virtual bool CanSetWindowBounds(const ServerWindow* window) const = 0;
   virtual bool CanSetWindowProperties(const ServerWindow* window) const = 0;
   virtual bool CanSetWindowTextInputState(const ServerWindow* window) const = 0;
   virtual bool CanSetCapture(const ServerWindow* window) const = 0;
   virtual bool CanSetFocus(const ServerWindow* window) const = 0;
   virtual bool CanSetClientArea(const ServerWindow* window) const = 0;
   virtual bool CanSetHitTestMask(const ServerWindow* window) const = 0;
   virtual bool CanSetAcceptDrops(const ServerWindow* window) const = 0;
   virtual bool CanSetAcceptEvents(const ServerWindow* window) const = 0;
+  virtual bool CanStackAbove(const ServerWindow* above,
+                             const ServerWindow* below) const = 0;
   virtual bool CanStackAtTop(const ServerWindow* window) const = 0;
   // Used for all client controllable cursor properties; which cursor should be
   // displayed, visibility, locking, etc.
   virtual bool CanSetCursorProperties(const ServerWindow* window) const = 0;
   virtual bool CanInitiateDragLoop(const ServerWindow* window) const = 0;
   virtual bool CanInitiateMoveLoop(const ServerWindow* window) const = 0;
 
   // Returns whether the client should notify on a hierarchy change.
   // |new_parent| and |old_parent| are initially set to the new and old parents
   // but may be altered so that the client only sees a certain set of windows.
   virtual bool ShouldNotifyOnHierarchyChange(
       const ServerWindow* window,
       const ServerWindow** new_parent,
       const ServerWindow** old_parent) const = 0;
   virtual bool CanSetWindowManager() const = 0;
 
   // Returns the window to supply to the client when focus changes to |focused|.
   virtual const ServerWindow* GetWindowForFocusChange(
       const ServerWindow* focused) = 0;
 
   virtual bool IsValidIdForNewWindow(const ClientWindowId& id) const = 0;
 };
 
 }  // namespace ws
 }  // namespace ui
 
 #endif  // SERVICES_UI_WS_ACCESS_POLICY_H_