Reland of "Apply Shelf/Dock opacity animations for the Material Design style."

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(int alpha) = 0;
+  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_