chromeos: convert remaining AshTest usage to AshTestBase

ash/mus/test/ash_test_impl_mus.h

Index: ash/mus/test/ash_test_impl_mus.h
diff --git a/ash/mus/test/ash_test_impl_mus.h b/ash/mus/test/ash_test_impl_mus.h
deleted file mode 100644
index 5e900aa3874ea87c60d59719635b037604d09c0a..0000000000000000000000000000000000000000
--- a/ash/mus/test/ash_test_impl_mus.h
+++ /dev/null
@@ -1,54 +0,0 @@
-// 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_MUS_TEST_ASH_TEST_IMPL_MUS_H_
-#define ASH_MUS_TEST_ASH_TEST_IMPL_MUS_H_
-
-#include "ash/mus/test/wm_test_base.h"
-#include "ash/test/ash_test_impl.h"
-#include "base/macros.h"
-
-namespace ash {
-namespace mus {
-
-class WmTestBase;
-
-// Implementation of AshTestImpl for mus.
-class AshTestImplMus : public AshTestImpl {
- public:
-  AshTestImplMus();
-  ~AshTestImplMus() override;
-
-  // AshTestImpl:
-  void SetUp() override;
-  void TearDown() override;
-  void UpdateDisplay(const std::string& display_spec) override;
-  std::unique_ptr<WindowOwner> CreateTestWindow(
-      const gfx::Rect& bounds_in_screen,
-      ui::wm::WindowType type,
-      int shell_window_id) override;
-  std::unique_ptr<WindowOwner> CreateToplevelTestWindow(
-      const gfx::Rect& bounds_in_screen,
-      int shell_window_id) override;
-  display::Display GetSecondaryDisplay() override;
-  bool SetSecondaryDisplayPlacement(
-      display::DisplayPlacement::Position position,
-      int offset) override;
-  void ConfigureWidgetInitParamsForDisplay(
-      WmWindow* window,
-      views::Widget::InitParams* init_params) override;
-  void AddTransientChild(WmWindow* parent, WmWindow* window) override;
-
- private:
-  // TODO(sky): fold WmTestBase directly into this class when no more subclasses
-  // of WmTestBase.
-  std::unique_ptr<WmTestBase> wm_test_base_;
-
-  DISALLOW_COPY_AND_ASSIGN(AshTestImplMus);
-};
-
-}  // namespace mus
-}  // namespace ash
-
-#endif  // ASH_MUS_TEST_ASH_TEST_IMPL_MUS_H_