Rename ash desktop_background to wallpaper.

ash/desktop_background/desktop_background_view.h

-// Copyright (c) 2012 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_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_VIEW_H_
-#define ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_VIEW_H_
-
-#include <memory>
-
-#include "ui/views/context_menu_controller.h"
-#include "ui/views/view.h"
-
-namespace ash {
-
-class PreEventDispatchHandler;
-class WmWindow;
-
-class DesktopBackgroundView : public views::View,
-                              public views::ContextMenuController {
- public:
-  DesktopBackgroundView();
-  ~DesktopBackgroundView() override;
-
- private:
-  friend class DesktopBackgroundControllerTest;
-
-  // Overridden from views::View:
-  void OnPaint(gfx::Canvas* canvas) override;
-  bool OnMousePressed(const ui::MouseEvent& event) override;
-
-  // Overridden from views::ContextMenuController:
-  void ShowContextMenuForView(views::View* source,
-                              const gfx::Point& point,
-                              ui::MenuSourceType source_type) override;
-  std::unique_ptr<PreEventDispatchHandler> pre_dispatch_handler_;
-
-  DISALLOW_COPY_AND_ASSIGN(DesktopBackgroundView);
-};
-
-views::Widget* CreateDesktopBackground(WmWindow* root_window, int container_id);
-
-}  // namespace ash
-
-#endif  // ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_VIEW_H_