It is time.

ui/compositor/layer_animator_collection.h

-// Copyright 2014 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_COMPOSITOR_LAYER_ANIMATOR_COLLECTION_H_
-#define UI_COMPOSITOR_LAYER_ANIMATOR_COLLECTION_H_
-
-#include <set>
-
-#include "base/callback.h"
-#include "base/memory/ref_counted.h"
-#include "base/time/time.h"
-#include "ui/compositor/compositor_animation_observer.h"
-#include "ui/compositor/compositor_export.h"
-
-namespace ui {
-
-class Compositor;
-class LayerAnimator;
-
-// A collection of LayerAnimators that should be updated at each animation step
-// in the compositor.
-class COMPOSITOR_EXPORT LayerAnimatorCollection
-    : public CompositorAnimationObserver {
- public:
-  explicit LayerAnimatorCollection(Compositor* compositor);
-  ~LayerAnimatorCollection() override;
-
-  void StartAnimator(scoped_refptr<LayerAnimator> animator);
-  void StopAnimator(scoped_refptr<LayerAnimator> animator);
-
-  bool HasActiveAnimators() const;
-
-  base::TimeTicks last_tick_time() const { return last_tick_time_; }
-
-  // CompositorAnimationObserver:
-  void OnAnimationStep(base::TimeTicks timestamp) override;
-
- private:
-  Compositor* compositor_;
-  base::TimeTicks last_tick_time_;
-  std::set<scoped_refptr<LayerAnimator> > animators_;
-
-  DISALLOW_COPY_AND_ASSIGN(LayerAnimatorCollection);
-};
-
-}  // namespace ui
-
-#endif  // UI_COMPOSITOR_LAYER_ANIMATOR_COLLECTION_H_