mash: Reverse the responsibilities of the NewWindowClient.

ash/common/test/wm_shell_test_api.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 "ash/common/test/wm_shell_test_api.h"
 
 #include <utility>
 
 #include "ash/common/system/tray/system_tray_delegate.h"
 #include "ash/common/wm_shell.h"
 #include "ash/public/interfaces/new_window.mojom.h"
 
 namespace ash {
 
 WmShellTestApi::WmShellTestApi() {}
 
 WmShellTestApi::~WmShellTestApi() {}
 
 void WmShellTestApi::SetSystemTrayDelegate(
     std::unique_ptr<SystemTrayDelegate> delegate) {
   WmShell::Get()->SetSystemTrayDelegate(std::move(delegate));
 }
 
-void WmShellTestApi::SetNewWindowClient(
-    std::unique_ptr<mojom::NewWindowClient> client) {
-  WmShell::Get()->new_window_client_ = std::move(client);
-}
-
 }  // namespace ash