Added a CallbackLayerAnimationObserver.

ui/compositor/callback_layer_animation_observer.h

Index: ui/compositor/callback_layer_animation_observer.h
diff --git a/ui/compositor/callback_layer_animation_observer.h b/ui/compositor/callback_layer_animation_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..9e966e08ecde91a289b739bc112bb20d273ae7e4
--- /dev/null
+++ b/ui/compositor/callback_layer_animation_observer.h
@@ -0,0 +1,137 @@
+// Copyright 2015 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_CALLBACK_LAYER_ANIMATION_OBSERVER_H_
+#define UI_COMPOSITOR_CALLBACK_LAYER_ANIMATION_OBSERVER_H_
+
+#include "base/callback.h"
+#include "ui/compositor/compositor_export.h"
+#include "ui/compositor/layer_animation_observer.h"
+
+namespace ui {
+
+class LayerAnimationSequence;
+
+// A LayerAnimationObserver that invokes a Callback when all observed
+// LayerAnimationSequence's have started and finished.
+//
+// Example usage:
+//  class Foobar {
+//    // The Callback that will be invoked when all the animation sequences have
+//    // started.
+//    void AnimationStartedCallback(
+//        const CallbackLayerAnimationObserver& observer) {
+//      // Do stuff.
+//    }
+//
+//    // The Callback that will be invoked when all the animation sequences have
+//    // finished.
+//    bool AnimationEndedCallback(
+//        const CallbackLayerAnimationObserver& observer) {
+//      // Do stuff.
+//      return true;  // Returns true so that |observer| destroys itself.
+//    }
+//
+//    // Example method that uses the CallbackLayerAnimationObserver.
+//    void Animate() {
+//      ui::LayerAnimator* animator_1 = layer_->GetAnimator();
+//      ui::LayerAnimator* animator_2 = layer_->GetAnimator();

[ajuma, 2015/10/07 20:14:55]

Should these by layer_1 and layer_2, not the same layer_ on both lines?
(Otherwise, animator_1 == animator_2.)

[bruthig, 2015/10/07 21:37:29]

Yes, good catch!

+//      CallbackLayerAnimationObserver* observer =
+//          new CallbackLayerAnimationObserver(
+//              base::Bind(&Foobar::AnimationStartedCallback),
+//              base::Unretained(this));
+//              base::Bind(&Foobar::AnimationEndedCallback),
+//              base::Unretained(this));
+//      animator_1->AddObserver(observer);
+//      animator_2->AddObserver(observer);
+//
+//      // Set up animation sequences on |animator_1| and |animator_2|.
+//
+//      // The callback won't be invoked until SetActive() is called.
+//      observer->SetActive();
+//    }
+//  }
+//
+class COMPOSITOR_EXPORT CallbackLayerAnimationObserver
+    : public ui::LayerAnimationObserver {
+ public:
+  // The Callback type that will be invoked when all animation sequences have
+  // been started.
+  typedef base::Callback<void(const CallbackLayerAnimationObserver&)>
+      AnimationStartedCallback;
+
+  // The Callback type that will be invoked when all animation sequences have
+  // finished. |this| will be destroyed after invoking the Callback if it
+  // returns true.
+  typedef base::Callback<bool(const CallbackLayerAnimationObserver&)>
+      AnimationEndedCallback;
+
+  explicit CallbackLayerAnimationObserver(

[bruthig, 2015/10/06 21:30:37]

TODO: Remove explicit.

[bruthig, 2015/10/07 21:37:29]

Done.

+      AnimationStartedCallback animation_started_callback,
+      AnimationEndedCallback animation_ended_callback);
+  ~CallbackLayerAnimationObserver() override;
+
+  bool active() const { return active_; }
+
+  // The callbacks will not be invoked until SetActive() has been called. This
+  // allows each sequence to be attached before checking if the sequences have
+  // finished.
+  void SetActive();
+
+  int aborted_count() const { return aborted_count_; }
+  int successful_count() const { return successful_count_; }
+
+  // ui::LayerAnimationObserver:
+  void OnLayerAnimationStarted(ui::LayerAnimationSequence* sequence) override;

[danakj, 2015/10/07 15:11:10]

This isn't a member of LayerAnimationObserver?

[bruthig, 2015/10/07 15:21:23]

It's being added in my pending CL here:
https://codereview.chromium.org/1381463002

+  void OnLayerAnimationEnded(ui::LayerAnimationSequence* sequence) override;
+  void OnLayerAnimationAborted(ui::LayerAnimationSequence* sequence) override;
+  void OnLayerAnimationScheduled(ui::LayerAnimationSequence* sequence) override;
+
+ protected:
+  // ui::LayerAnimationObserver:
+  bool RequiresNotificationWhenAnimatorDestroyed() const override;
+  void OnAttachedToSequence(ui::LayerAnimationSequence* sequence) override;
+  void OnDetachedFromSequence(ui::LayerAnimationSequence* sequence) override;
+
+ private:
+  int GetNumSequencesCompleted();
+
+  // Checks if all attached sequences have been started and invokes
+  // |animation_started_callback_| if |active_| is true.
+  void CheckAllSequencesStarted();
+
+  // Checks if all attached sequences have completed and invokes
+  // |animation_ended_callback_| if |active_| is true.
+  void CheckAllSequencesCompleted();
+
+  // Allows the callbacks to be invoked when true.
+  bool active_;
+
+  // The total number of animation sequences that have been attached.
+  int attached_sequence_count_;
+
+  // The total number of animation sequences that have been detached.
+  int detached_sequence_count_;
+
+  // The number of animation sequences that have been started.
+  int started_count_;
+
+  // The number of animation sequences that were aborted.
+  int aborted_count_;
+
+  // The number of animation sequences that completed successfully.
+  int successful_count_;
+
+  // The callback to invoke once all the animation sequences have been started.
+  AnimationStartedCallback animation_started_callback_;
+
+  // The callback to invoke once all the animation sequences have finished.
+  AnimationEndedCallback animation_ended_callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(CallbackLayerAnimationObserver);
+};
+
+}  // namespace ui
+
+#endif  // UI_COMPOSITOR_CALLBACK_LAYER_ANIMATION_OBSERVER_H_