Rename ash desktop_background to wallpaper.

ash/wm/system_background_controller.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_WM_SYSTEM_BACKGROUND_CONTROLLER_H_
-#define ASH_WM_SYSTEM_BACKGROUND_CONTROLLER_H_
-
-#include <memory>
-#include <string>
-
-#include "ash/ash_export.h"
-#include "base/macros.h"
-#include "third_party/skia/include/core/SkColor.h"
-#include "ui/aura/window_observer.h"
-
-namespace ui {
-class Layer;
-}
-
-namespace ash {
-
-// SystemBackgroundController manages a ui::Layer that's stacked at the bottom
-// of an aura::RootWindow's children.  It exists solely to obscure portions of
-// the root layer that aren't covered by any other layers (e.g. before the
-// desktop background image is loaded at startup, or when we scale down all of
-// the other layers as part of a power-button or window-management animation).
-// It should never be transformed or restacked.
-class SystemBackgroundController : public aura::WindowObserver {
- public:
-  SystemBackgroundController(aura::Window* root_window, SkColor color);
-  ~SystemBackgroundController() override;
-
-  void SetColor(SkColor color);
-
-  // aura::WindowObserver overrides:
-  void OnWindowBoundsChanged(aura::Window* root,
-                             const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
-
- private:
-  class HostContentLayerDelegate;
-
-  aura::Window* root_window_;  // not owned
-
-  std::unique_ptr<ui::Layer> layer_;
-
-  DISALLOW_COPY_AND_ASSIGN(SystemBackgroundController);
-};
-
-}  // namespace ash
-
-#endif  // ASH_WM_SYSTEM_BACKGROUND_CONTROLLER_H_