mash: Move directly linked NewWindowDelegate to mojom::NewWindowClient.

ash/common/test/wm_shell_test_api.h

 // 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.
 
 #ifndef ASH_COMMON_TEST_WM_SHELL_TEST_API_H_
 #define ASH_COMMON_TEST_WM_SHELL_TEST_API_H_
 
 #include <memory>
 
 #include "base/macros.h"
 
 namespace ash {
 
 class SystemTrayDelegate;
 
+namespace mojom {
+class NewWindowClient;
+}
+
 // Test API to access the internal state of the singleton WmShell.
 class WmShellTestApi {
  public:
   WmShellTestApi();
   ~WmShellTestApi();
 
   void SetSystemTrayDelegate(std::unique_ptr<SystemTrayDelegate> delegate);
 
+  void SetNewWindowClient(std::unique_ptr<mojom::NewWindowClient> client);
+
  private:
   DISALLOW_COPY_AND_ASSIGN(WmShellTestApi);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_TEST_WM_SHELL_TEST_API_H_