Remove (Native)Widget::StackBelow().

ui/views/mus/native_widget_mus.h

 // Copyright 2015 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 UI_VIEWS_MUS_NATIVE_WIDGET_MUS_H_
 #define UI_VIEWS_MUS_NATIVE_WIDGET_MUS_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 124 matching lines @@
                       const gfx::ImageSkia& app_icon) override;
   void InitModalType(ui::ModalType modal_type) override;
   gfx::Rect GetWindowBoundsInScreen() const override;
   gfx::Rect GetClientAreaBoundsInScreen() const override;
   gfx::Rect GetRestoredBounds() const override;
   std::string GetWorkspace() const override;
   void SetBounds(const gfx::Rect& bounds_in_screen) override;
   void SetSize(const gfx::Size& size) override;
   void StackAbove(gfx::NativeView native_view) override;
   void StackAtTop() override;
-  void StackBelow(gfx::NativeView native_view) override;
   void SetShape(std::unique_ptr<SkRegion> shape) override;
   void Close() override;
   void CloseNow() override;
   void Show() override;
   void Hide() override;
   void ShowMaximizedWithBounds(const gfx::Rect& restored_bounds) override;
   void ShowWithWindowState(ui::WindowShowState state) override;
   bool IsVisible() const override;
   void Activate() override;
   void Deactivate() override;
@@ skipping 145 matching lines @@
   int last_drop_operation_;
 
   base::WeakPtrFactory<NativeWidgetMus> close_widget_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeWidgetMus);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_MUS_NATIVE_WIDGET_MUS_H_