[ash-md] Remove the number of animators used for the Shelf animations.

ash/common/wm/background_animator.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_COMMON_WM_BACKGROUND_ANIMATOR_H_
-#define ASH_COMMON_WM_BACKGROUND_ANIMATOR_H_
-
-#include "ash/ash_export.h"
-#include "base/macros.h"
-#include "ui/gfx/animation/animation_delegate.h"
-#include "ui/gfx/animation/slide_animation.h"
-
-namespace ash {
-
-// How the background can be changed.
-enum BackgroundAnimatorChangeType {
-  BACKGROUND_CHANGE_ANIMATE,
-  BACKGROUND_CHANGE_IMMEDIATE
-};
-
-class BackgroundAnimator;
-
-// Delegate is notified any time the background changes.
-class ASH_EXPORT BackgroundAnimatorDelegate {
- public:
-  virtual void UpdateBackground(BackgroundAnimator* animator, int alpha) = 0;
-
-  virtual void BackgroundAnimationEnded(BackgroundAnimator* animator) = 0;
-
- protected:
-  virtual ~BackgroundAnimatorDelegate() {}
-};
-
-// BackgroundAnimator is used by the shelf to animate the background (alpha).
-class ASH_EXPORT BackgroundAnimator : public gfx::AnimationDelegate {
- public:
-  BackgroundAnimator(BackgroundAnimatorDelegate* delegate,
-                     int min_alpha,
-                     int max_alpha);
-  ~BackgroundAnimator() override;
-
-  // Sets the transition time in ms.
-  void SetDuration(int time_in_ms);
-
-  // Stops the animation. Does nothing if the animation is not running.
-  void Stop();
-
-  // Sets whether a background is rendered. Initial value is false. If |type|
-  // is |CHANGE_IMMEDIATE| and an animation is not in progress this notifies
-  // the delegate immediately (synchronously from this method).
-  void SetPaintsBackground(bool value, BackgroundAnimatorChangeType type);
-  bool paints_background() const { return paints_background_; }
-
-  // Current alpha.
-  int alpha() const { return alpha_; }
-
-  // gfx::AnimationDelegate overrides:
-  void AnimationProgressed(const gfx::Animation* animation) override;
-  void AnimationEnded(const gfx::Animation* animation) override;
-
- private:
-  BackgroundAnimatorDelegate* delegate_;
-
-  const int min_alpha_;
-  const int max_alpha_;
-
-  gfx::SlideAnimation animation_;
-
-  // Whether the background is painted.
-  bool paints_background_;
-
-  // Current alpha value of the background.
-  int alpha_;
-
-  DISALLOW_COPY_AND_ASSIGN(BackgroundAnimator);
-};
-
-}  // namespace ash
-
-#endif  // ASH_COMMON_WM_BACKGROUND_ANIMATOR_H_