aura-mus: Make StackAtTop() proxy to the window manager.

services/ui/ws/test_utils.cc

 // Copyright 2016 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.
 
 #include "services/ui/ws/test_utils.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "cc/output/copy_output_request.h"
@@ skipping 229 matching lines @@
                                           uint32_t window_id,
                                           mojom::MoveLoopSource source,
                                           const gfx::Point& cursor_location) {
   on_perform_move_loop_called_ = true;
 }
 
 void TestWindowManager::WmCancelMoveLoop(uint32_t window_id) {}
 
 void TestWindowManager::WmDeactivateWindow(uint32_t window_id) {}
 
+void TestWindowManager::WmStackAtTop(uint32_t change_id, uint32_t window_id) {}
+
 void TestWindowManager::OnAccelerator(uint32_t ack_id,
                                       uint32_t accelerator_id,
                                       std::unique_ptr<ui::Event> event) {
   on_accelerator_called_ = true;
   on_accelerator_id_ = accelerator_id;
 }
 
 // TestWindowTreeClient -------------------------------------------------------
 
 TestWindowTreeClient::TestWindowTreeClient()
@@ skipping 373 matching lines @@
     return nullptr;
   if (!tree->AddWindow(parent_client_id, client_window_id))
     return nullptr;
   *client_id = client_window_id;
   return tree->GetWindowByClientId(client_window_id);
 }
 
 }  // namespace test
 }  // namespace ws
 }  // namespace ui