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

services/ui/ws/window_tree.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_WINDOW_TREE_H_
 #define SERVICES_UI_WS_WINDOW_TREE_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 427 matching lines @@
   void OnWindowInputEventAck(uint32_t event_id,
                              mojom::EventResult result) override;
   void DeactivateWindow(Id window_id) override;
   void SetClientArea(Id transport_window_id,
                      const gfx::Insets& insets,
                      const base::Optional<std::vector<gfx::Rect>>&
                          transport_additional_client_areas) override;
   void SetCanAcceptDrops(Id window_id, bool accepts_drops) override;
   void SetHitTestMask(Id transport_window_id,
                       const base::Optional<gfx::Rect>& mask) override;
+  void StackAbove(uint32_t change_id, Id above_id, Id below_id) override;
   void StackAtTop(uint32_t change_id, Id window_id) override;
   void GetWindowManagerClient(
       mojo::AssociatedInterfaceRequest<mojom::WindowManagerClient> internal)
       override;
   void GetCursorLocationMemory(const GetCursorLocationMemoryCallback& callback)
       override;
   void PerformDragDrop(
       uint32_t change_id,
       Id source_window_id,
       const std::unordered_map<std::string, std::vector<uint8_t>>& drag_data,
@@ skipping 122 matching lines @@
       waiting_for_top_level_window_info_;
   bool embedder_intercepts_events_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(WindowTree);
 };
 
 }  // namespace ws
 }  // namespace ui
 
 #endif  // SERVICES_UI_WS_WINDOW_TREE_H_